staging: r8188eu: Prefer kcalloc over kzalloc

staging: r8188eu: Prefer kcalloc over kzalloc

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

Instead of specifying (number of bytes) * (size) as arugment
in kzalloc, prefer kcalloc.

Signed-off-by: Kang Minchul <tegongkang@gmail.com>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Reviewed-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20221216223942.334221-1-tegongkang@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>