bcm2838_xhci: add module

bcm2838_xhci(4) is a shim for the XHCI controller on the Raspberry Pi 4B
SoC. It loads the controller's firmware before passing control to the
normal xhci(4) driver.

When xhci(4) is built as a module (and not in the kernel), bcm2838_xhci
is not built at all and the RPi4's XHCI controller won't attach due to
missing firmware.

To fix this, build a new module, bcm2838_xhci.ko, which depends on
xhci.ko. For the dependency to work correctly, also modify xhci to
provide the 'xhci' module in addition to the 'xhci_pci' module it
already provided.

Since bcm2838_xhci is specific to a quirk of the RPi4 SoC, only build
the module for AArch64.

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1142

sys: Remove $FreeBSD$: one-line .c pattern

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

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

arm/arm64 broadcom: Remove unused devclass arguments to DRIVER_MODULE.

Add the missing terminator to the bcm_xhci methods

Sponsored by: The FreeBSD Foundation

arm: clean up empty lines in .c and .h files

Handle Raspberry Pi 4 xhci firmware loading.

The newer hardware revisions of the Raspberry Pi 4 removed the ability of
the VIA VL805 xhci controller to load its own firmware. Instead the
firmware must be installed at the appropriate time by the VideoCore
coprocessor.

Submitted by: Robert Crowston <crowston_protonmail.com>
Differential Revision: https://reviews.freebsd.org/D25261