firmware: arm_scmi: remove redundant null check on array

The null check on clk->name is redundant since name is a char array
and can never be null, so the check is always true.  Remove it.

Detected by CoverityScan, CID#1466117 ("Array compared against 0")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>