gpu: host1x: remove redundant assignment to variable space

The variable space is being initialized with a value that is never read,
it is being re-assigned later on. The initialization is redundant and
can be removed. Also merge two declaration lines together.

Cleans up clang scan build warning:
drivers/gpu/host1x/cdma.c:628:15: warning: Value stored to 'space'
during its initialization is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240215224301.2073845-1-colin.i.king@gmail.com