mm/cma: fix useless return in void function

There is a unnecessary return statement at the end of void function
cma_activate_area.  This can be dropped.

While at it, also fix another warning related to unsigned.
These are reported by checkpatch as well.

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
+unsigned cma_area_count;

WARNING: void function return statements are not generally useful
+       return;
+}

Link: https://lkml.kernel.org/r/20240927181637.19941-1-quic_pintu@quicinc.com


Signed-off-by: Pintu Kumar <quic_pintu@quicinc.com>
Cc: Pintu Agarwal <pintu.ping@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>