soc: fsl: qe: move qe_ic_cascade_* functions to qe_ic.c

These functions are only ever called through a function pointer, and
therefore it makes no sense for them to be "static inline" - gcc has
no choice but to emit a copy in each translation unit that takes the
address of one of these. Since they are now only referenced from
qe_ic.c, just make them local to that file.

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