mxs: Reset the EMI block on mx23

mxs: Reset the EMI block on mx23

The real reason for memory instability was the fact that the EMI block
was gated and not reset throughout the boards' operation. This patch
resets the EMI block properly while also reverts the memory voltage bump.
The memory stability issues were caused by the EMI not being reset properly
and thus there is no longer need to run the memory at higher voltage than
it ought to run at.

This partly reverts 8303ed128a55519f19c5f11087032d4bc4e0537a .

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>