sh: use in-soc KEYSC on se7724

This patch updates the Solution Engine 7724 board code to use
in-SoC KEYSC resources for the keyboard platform device. Using
the in-SoC key scan controller fixes a crash-during-resume issue.

Without this patch the KEYSC hardware block located in the board
specific FPGA is used together with an external IRQ which is
routed through the FPGA and handled by some board specific demux
code. This board specific FPGA interrupt code does not implement
desc->set_wake() so the enable_irq_wake() call in the sh_keysc
driver will fail at suspend-to-ram time and the disable_irq_wake()
will bomb out when resuming.

Changing the platform data to use the in-SoC KEYSC hardware makes
the se7724 board support code less special which is a good thing.
Also, the board specific KEYSC pin setup code selects in-SoC pin
functions already which makes the current FPGA platform device data
look like a typo.

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