avoid various seemingly bogus warnings with GCC 14.

i couldn't see any real case for any of these issues. it seems like
the "maybe uninit" checker has gotten worse.

additionally, the "dangling pointer" checker also failing.

drm: Set CONFIG_ACPI in linux/acpi.h and make it build.

Leave a little ACPI-related functionality disabled for now, like
getting EDID out of ACPI -- needs a bit more work to make this work,
and I don't have hardware to work on that.

Should help with failures of the forms:

- unable to locate a BIOS ROM
- bios: unable to locate usable image

on various machines.

use CC_WNO_MAYBE_UNINITIALIZED and fix the clang build.

apply some warning disables for GCC 12.

*possibly* the one for intel_dp.c is a real bug but it seems very
difficult to be sure (i can't seem to convince myself either way.)

amdgpu: Define CONFIG_DRM_AMD_DC to enable display core logic.

Probably resolves a host of issues with amdgpu not detecting
displays!

Noticed by rjs@.

PR kern/57059
PR kern/57325
PR kern/57452

XXX pullup-10

branches: 1.5.4;
COPTS -> CWARNFLAGS

amdgpu: add some more CWARNFLAGS to appease clang

XXX backport this change to files.amdgpu

amdgpu: don't set -mhard-float for clang

clang complains that the option has no effect and it generates hard
float instructions without the option. soft-float not really supported
on x86_64 with clang from what I can tell.

amdgpu: Sprinkle missing COPTS.amdgpu_float options.

For some reason x86 didn't need these but aarch64 does.

amdgpu: New kernel module build goo.