spi: spi_qsd: Fix unclocked register access in set_cs function

Fix an unclocked register access during the set_cs() function
call from the framework.
This case happens when a QUP core is marked as shared between
different execution environments and there is an attempt to perform
IO operations pertaining to CS without enabling the required clocks.

Change-Id: I7d0eb027252fbecac21f4244cdba18ec31e301fc
Acked-by: Neo Choe <nchoe@qti.qualcomm.com>
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>