mmc: renesas_sdhi_internal_dmac: fix #define RST_RESERVED_BITS

The DM_CM_RST register actually has bits 0-31 defaulting to 1s and bits
32-63 defaulting to 0s -- fix off-by-one in #define RST_RESERVED_BITS.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Fixes: 2a68ea78

 ("mmc: renesas-sdhi: add support for R-Car Gen3 SDHI DMAC")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>