Staging: greybus: light: Prefer kcalloc over kzalloc

Fixed following checkpatch.pl warning:
 * WARNING: Prefer kcalloc over kzalloc with multiply

Instead of specifying no.of bytes * size as argument
in kzalloc, prefer kcalloc.

Signed-off-by: Karthik Tummala <karthik@techveda.org>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Changes for v2:
- Changed subject line & fixed typo as suggested by
  Rui Miguel Silva
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>