drm/lsdc: Request PCI BAR

lsdc currently just ioremaps its PCI BAR with pcim_iomap(). Performing
a region regquest additionally can make the driver more robust.

Replace pcim_iomap() with the managed function pcim_iomap_region() which
performs the request and ioremaps the BAR.

Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Reviewed-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Link: https://patchwork.freedesktop.org/patch/msgid/20241021091116.14368-1-pstanner@redhat.com