drm/msm/dpu: invalid parameter check in dpu_setup_dspp_pcc

drm/msm/dpu: invalid parameter check in dpu_setup_dspp_pcc

BugLink: https://bugs.launchpad.net/bugs/1959879
[ Upstream commit 170b22234d5495f5e0844246e23f004639ee89ba ]

The function performs a check on the "ctx" input parameter, however, it
is used before the check.

Initialize the "base" variable after the sanity check to avoid a
possible NULL pointer dereference.

Fixes: 4259ff7ae509e ("drm/msm/dpu: add support for pcc color block in dpu driver")
Addresses-Coverity-ID: 1493866 ("Null pointer dereference")
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Link: https://lore.kernel.org/r/20220109192431.135949-1-jose.exposito89@gmail.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>