soc: fsl: qe: make cpm_muram_free() return void

Nobody uses the return value from cpm_muram_free, and functions that
free resources usually return void. One could imagine a use for a "how
much have I allocated" a la ksize(), but knowing how much one had
access to after the fact is useless.

Reviewed-by: Timur Tabi <timur@kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Li Yang <leoyang.li@nxp.com>