soc: fsl: qe: qe.c: guard use of pvr_version_is() with CONFIG_PPC32

Commit e5c5c8d2 (soc/fsl/qe: only apply QE_General4 workaround on
affected SoCs) introduced use of pvr_version_is(), saying

    The QE_General4 workaround is only valid for the MPC832x and MPC836x
    SoCs. The other SoCs that embed a QUICC engine are not affected by this
    hardware bug and thus can use the computed divisors (this was
    successfully tested on the T1040).

I'm reading the above as saying that the errata does not apply to the
ARM-based SOCs with QUICC engine. In any case, use of pvr_version_is()
must be guarded by CONFIG_PPC32 before we can remove the PPC32
dependency from CONFIG_QUICC_ENGINE, so introduce qe_general4_errata()
to keep the necessary #ifdeffery localized to a trivial helper.

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