memory: renesas-rpc-if: Drop usage of RPCIF_DIRMAP_SIZE macro

RPCIF_DIRMAP_SIZE may differ on various SoC's. Instead of using
RPCIF_DIRMAP_SIZE macro use resource size to get dirmap size
which is already part of struct rpcif.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20211025205631.21151-7-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>