drm/lima: include used header file explicitly

To prevent build fail on some platform which does
not have it in the include file chain.

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Suggested-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: a1d2a633

 ("drm/lima: driver for ARM Mali4xx GPUs")
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190409003617.4470-2-yuq825@gmail.com