msm: footswitch-8x60: Move SoC-specific data to device files

The number of footswitch-related differences between SoCs (such as clocks
and bus ports) is large enough that it no longer makes sense to treat
them as exceptions in footswitch_probe().

Instead of using cpu_is_xxx() to manage these differences, move all
SoC-specific data to the SoC-specific device files and pass it to the
footswitch driver through platform data.

Change-Id: I30e2ec885e0340e4efec2bc5adc3fdd255cc7bb0
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>