soc: fsl: qe: drop volatile qualifier of struct qe_ic::regs

The actual io accessors (e.g. in_be32) implicitly add a volatile
qualifier to their address argument. Remove volatile from the struct
definition and the qe_ic_(read/write) helpers, in preparation for
switching from the ppc-specific io accessors to generic ones.

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