DT: mmc: sh_mmcif: fix "compatible" property text

The "compatible" property text contradicts even the example given in the MMCIF
binding document itself;  moreover, the Renesas MMCIF driver only matches  on
the generic "compatible" string and doesn't look for the SoC specific strings
at all. Thus describe "renesas,sh-mmcif" as a fallback value.

Fixes: b4c27763 ("mmc: sh_mmcif: Document DT bindings")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>