gpu: host1x: select CONFIG_DMA_SHARED_BUFFER

Linking fails when dma-buf is disabled:

ld.lld: error: undefined symbol: dma_fence_release
>>> referenced by fence.c
>>>               gpu/host1x/fence.o:(host1x_syncpt_fence_enable_signaling) in archive drivers/built-in.a
>>> referenced by fence.c
>>>               gpu/host1x/fence.o:(host1x_fence_signal) in archive drivers/built-in.a
>>> referenced by fence.c
>>>               gpu/host1x/fence.o:(do_fence_timeout) in archive drivers/built-in.a

Fixes: 687db220

 ("gpu: host1x: Add DMA fence implementation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>