ARC: Cache: Move SLC status check into slc_entire_op() and slc_rgn_op()

ARC: Cache: Move SLC status check into slc_entire_op() and slc_rgn_op()

As of today we check SLC status before each call of __slc_rgn_op()
or __slc_entire_op(). So move status check into __slc_rgn_op()
and __slc_entire_op().

As we need to check status before *each* function execution and we
call slc_entire_op() and slc_rgn_op() from different places we add
this check directly into SLC entire/line functions instead of
their callers to avoid code duplication.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>