uboot-imx

mxs: Add function to ungate the power block on MX23

The power block on MX23 must first be ungated before it can be operated.
Add function to MXS power init that ungates it.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Stefano Babic <sbabic@denx.de>