Revert "regulator: Add regmap helper for ramp-delay setting"

This reverts commit 12cb97ed which is
commit fb8fee9e upstream.

It is part of a series that breaks the Android kernel abi and can be
safely reverted at this point in time.  If it needs to come back in the
future, it can be done so in an abi-safe way.

Bug: 161946584
Change-Id: I8b912fb1cd2aa9e0ebfba10aaba93a147a32815b
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>