libsa: Remove redundant sys/cdefs.h

Sponsored by: Netflix

loader: fix EFI ACPI detection

lua was previously unable to determine ACPI presence because this
probing was postponed until the final loading and execution of the
kernel.

This patch resolves that by detecting ACPI early (similar to
the order of operations in the legacy i386 loader).

Reviewed by: kevans
Approved by: kp
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D42459

Remove $FreeBSD$: one-line .c pattern

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

Note that static hints no longer break loader hints

This commentary was carried over from the x86 version of the same code,
but has actually been inaccurate for a while now. As of FreeBSD 12.x,
all environments are used unless they disable each other. See
39d44f7f15c ("kern_environment: use any provided environments [...]")
for details.

Reviewed by: imp
Differentiala Revision: https://reviews.freebsd.org/D35695

loader: Set preferred kenv for acpi.rsdp on arm64

Several years ago, x86 moved from using hints to communicate this
information to using the simpler acpi.rsdp variables. If one compiles
static hints into the kernel, then these hints are ignored. We can
remove this when we branch FreeBSD 15. Thought about BURN_BRIDGES
here, but it's too messy.

Sponsored by: Netflix
Reviewed by: andrew, jhb
Differential Revision: https://reviews.freebsd.org/D35632

Don't sync the I/D caches when they are coherent

In the arm64 loader we need to syncronise the I and D caches. On some
newer CPUs the I and D caches are coherent so we don't need to perform
these operations.

While here remove the arguments to cpu_inval_icache as they are unneeded.

Reported by: cperciva
Tested by: cperciva
Sponsored by: Innovate UK

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

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix