sh: Remove unused WP signal for SDHI0 and KFR2R09

Get rid of the unused WP signal for SDHI0 on KFR2R09.
This because yc304 on KFR2R09 is a Micro SD slot which
does not implement the WP signal.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>