drm/msm/mdp5: Remove set but not used variable 'fmt'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/msm/disp/mdp5/mdp5_smp.c: In function mdp5_smp_calculate:
drivers/gpu/drm/msm/disp/mdp5/mdp5_smp.c:134:6: warning: variable fmt set but not used [-Wunused-but-set-variable]

It is not used since commit 24c478ea ("drm/fourcc:
Pass the format_info pointer to drm_format_plane_cpp")

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1570690506-83287-2-git-send-email-zhengbin13@huawei.com