remoteproc/mediatek: fix null pointer dereference on null scp pointer

remoteproc/mediatek: fix null pointer dereference on null scp pointer

Currently when pointer scp is null a dev_err is being called that
references the pointer which is the very thing we are trying to
avoid doing. Remove the extraneous error message to avoid this
issue.

Addresses-Coverity: ("Dereference after null check")
Fixes: 7cca6d2e214d ("remoteproc/mediatek: add SCP support for mt8183")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20200918152428.27258-1-colin.king@canonical.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>