[gta02-core] PMU cleanup

[Álvaro Lopes]

Hi,

Besides all "cleanup" issues we discussed about PMU, I think we might go a bit farther. I also found some "inconsistencies".

* GSM_ON is a global label, but only used inside PMU. We should switch to a local label, and maybe move R1729 near U1703.

* nGSM_OC is not used any more ? It was connected to EINT19, but due to ECN0001, we are using this GPIO for board revision check. What was the purpose of this
signal ?

* LDO4, LDO5 and LDO6 have buffer caps (4u7), but LDO1 and LDO2 do not. Any particular reason ?

Álvaro