drm/amdgpu: rename amdgpu_device_is_px to amdgpu_device_supports_boco (v2)

BACO - Bus Active, Chip Off
BOCO - Bus Off, Chip Off

To better match what we are checking for and to align with
amdgpu_device_supports_baco.

BOCO is used on PowerXpress/Hybrid Graphics systems and BACO
is used on desktop dGPU boards.

v2: fix typo in documentation

Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>