spi: rpc-if: Gaurd .pm assignment with CONFIG_PM_SLEEP #ifdef check

With CONFIG_PM_SLEEP disabled the rpcif_spi_pm_ops variable is still
referenced and thus increasing the size of kernel.

Fix this issue by adding CONFIG_PM_SLEEP #ifdef check around the .pm
assignment (image size is critical on RZ/A SoC's where the SRAM sizes
range 4~5 MiB).

Fixes: 9584fc95 ("spi: rpc-if: Remove CONFIG_PM_SLEEP ifdefery")
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Suggested-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20210107145329.27966-1-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>