ARM: mach-shmobile: kzm9g: do not enable REGULATOR_DUMMY in defconfig

Don't enable REGULATOR_DUMMY, it is only intended for development / testing.
There doesn't seem to be any value in setting it here and doing
so was an error on my part.

Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>