regulator: fixed/gpio: Revert GPIO descriptor changes due to platform breakage

Commit 6059577c "regulator: fixed: Convert to use GPIO descriptor
only" broke at least the ams-delta platform since the lookup tables
added to the board files use the function name "enable" while the driver
uses NULL causing the regulator to not acquire and control the enable
GPIOs.  Revert that and a couple of other commits that are caught up
with it to fix the issue:

2b6c00c1 "ARM: pxa, regulator: fix building ezx e680"
6059577c "regulator: fixed: Convert to use GPIO descriptor only"
37bed97f "regulator: gpio: Get enable GPIO using GPIO descriptor"
Reported-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>