MAINTAINERS: adjust to reservation.h renaming

Commit 52791eee

 ("dma-buf: rename reservation_object to dma_resv")
renamed include/linux/reservation.h to include/linux/dma-resv.h, but
missed the reference in the MAINTAINERS entry.

Since then, ./scripts/get_maintainer.pl --self-test complains:

  warning: no file matches F: include/linux/reservation.h

Adjust the DMA BUFFER SHARING FRAMEWORK entry in MAINTAINERS.

Co-developed-by: Sebastian Duda <sebastian.duda@fau.de>
Signed-off-by: Sebastian Duda <sebastian.duda@fau.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/356414/


Signed-off-by: Christian König <christian.koenig@amd.com>