drm/amdkfd: Add bounds check for CRAT subtype length

drm/amdkfd: Add bounds check for CRAT subtype length

The CRAT parser validates that the subtype header fits within the image,
but does not verify that the advertised subtype length fits. A malformed
CRAT table with an oversized length field causes out-of-bounds reads when
kfd_parse_subtype() casts the header to specific subtype structures.

Add validation that sub_type_hdr + length does not exceed the image
boundary before parsing the subtype contents.

Signed-off-by: William Palacek <William.Palacek@amd.com>
Reviewed-by: Alysa Liu <Alysa.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 48e1d1e6e8798aef0312e68d8e586021b5b3cf4d)
Cc: stable@vger.kernel.org