drm/ttm: Make the call to ttm_tt_populate() interruptible when faulting

When swapping in, or under memory pressure ttm_tt_populate() may sleep
for a substantiable amount of time. Allow interrupts during the sleep.
This will also allow us to inject -EINTR errors during swapin in upcoming
patches.

Also avoid returning VM_FAULT_OOM, since that will confuse the core
mm, making it print out a confused message and retrying the fault.
Return VM_FAULT_SIGBUS also under OOM conditions.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230404200650.11043-4-thomas.hellstrom@linux.intel.com