msm: footswitch-8x60: Skip GFX memory power collapse on 8064

Update footswitch_disable to skip GFX memory power collapse on
8064 to avoid any voltage droop on vddmx during GFX3D footswitch
toggling.

As per hardware designer recommendations this would help to
improve system stability when responding to the inrush current
event.

Change-Id: Ifa2f62629f0639d29f882d009dc5f4c10da46ca8
Signed-off-by: Shashank Mittal <mittals@codeaurora.org>