stand: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

stand/efi: allow not exiting boot services

Xen requires that UEFI BootServices are enabled in order to boot, so
introduce a new parameter to bi_load in order to select whether BS
should be exited.

No functional change introduced in this patch, as all current users of
bi_load request BS to be exited. Further changes will make use of this
functionality.

Note the memory map is still appended to the kernel metadata, even
when it could be modified by further calls to the Boot Services, as it
will be used to detect if the kernel has been booted from UEFI.

Sponsored by: Citrix Systems R&D
Reviewed by: tsoome, imp
Differential revision: https://reviews.freebsd.org/D28495

loader: Avoid -Wpointer-to-int cast warnings for Arm and RISC-V

On RISC-V, Clang warns with:

cast to smaller integer type 'unsigned int' from 'void (*)(void *)'

Instead, use %p as the standard format specifier for printing pointers.
Whilst Arm's pointer size is the same as unsigned, it's still cleaner to
use the right thing there too.

Reviewed by: brooks (mentor), emaste
Approved by: brooks (mentor), emaste
Differential Revision: https://reviews.freebsd.org/D25718

RISC-V boot1.efi and loader.efi support

This implementation doesn't have any major deviations from the other EFI
ports. I've copied the boilerplate from arm and arm64.

I've tested this with the following boot flows:
OpenSBI (M-mode) -> u-boot (S-mode) -> loader.efi -> FreeBSD
OpenSBI (M-mode) -> u-boot (S-mode) -> boot1.efi -> loader.efi -> FreeBSD

Due to the way that u-boot handles secondary CPUs, OpenSBI >= v0.7 is required,
as the HSM extension is needed to bring them up explicitly. Because of this,
using BBL as the SBI implementation will not be possible. Additionally, there
are a few recent u-boot changes that are required as well, all of which will be
present in the upcoming v2020.07 release.

Looks good: emaste
Differential Revision: https://reviews.freebsd.org/D25135