memory: renesas-rpc-if: Make rpcif_enable/disable_rpm() as static inline

Define rpcif_enable_rpm() and rpcif_disable_rpm() as static
inline in the header instead of exporting them.

Suggested-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Pavel Machek (CIP) <pavel@denx.de>
Link: https://lore.kernel.org/r/20201126191146.8753-5-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>