drm/amdgpu: add read_bios_from_rom callback for CI parts

drm/amdgpu: add read_bios_from_rom callback for CI parts

BugLink: http://bugs.launchpad.net/bugs/1546572
Read the vbios image directly from the rom.

Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Monk Liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 1eb22bd38ac58a1be6e7e0ae6dd4ab6d604a27d6)
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>