sh: fix R2D-1 CF support

This patch fixes CF support for R2D-1 boards. Both R2D-1 and
R2D-PLUS are equipped with CF IRQs, but the R2D-1 FPGA version
seem to deliver IRQ spikes with certain CF cards during libata
probing.  This patch enables polling for R2D-1 as a workaround
for this broken FGPA logic.

R2D-1 CF support was recently introduced by commit:
43f4b8c7

.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>