drm/panfrost: Remove incorrect IS_ERR() check

sg_page_iter_page() doesn't return an error code, so the IS_ERR() check
is wrong and the error path will never be executed. This also allows
simplifying the code to remove the local variable 'page'.

CC: Adrián Larumbe <adrian.larumbe@collabora.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/376713ff-9a4f-4ea3-b097-fb5efb685d95@moroto.mountain
Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Tested-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231020104405.53992-1-steven.price@arm.com

drm/gem: Take reservation lock for vmap/vunmap operations

The new common dma-buf locking convention will require buffer importers
to hold the reservation lock around mapping operations. Make DRM GEM core
to take the lock around the vmapping operations and update DRM drivers to
use the locked functions for the case where DRM core now holds the lock.
This patch prepares DRM core and drivers to the common dynamic dma-buf
locking convention.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221017172229.42269-4-dmitry.osipenko@collabora.com

drm/panfrost: replace endian-specific types with native ones

__le32 and __le64 types aren't portable and are not available on
FreeBSD (which uses the same uAPI).

Instead of attempting to always output little endian, just use native
endianness in the dumps. Tools can detect the endianness in use by
looking at the 'magic' field, but equally we don't expect big-endian to
be used with Mali (there are no known implementations out there).

Bug: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7252
Fixes: 730c2bf4ad39 ("drm/panfrost: Add support for devcoredump")
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221017104602.142992-3-steven.price@arm.com

drm/panfrost: Add support for devcoredump

In the event of a job timeout, debug dump information will be written into
/sys/class/devcoredump.

Inspired by etnaviv's similar feature.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220729144610.2105223-3-adrian.larumbe@collabora.com