regulator: Unsupport 88pm8607 A0 and A1

Remove the support 88PM8607 A0/A1 stepping. There's some register
definition changes in B0 stepping. It can make software more efficient.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>