Convert CONFIG_NORFLASH_PS32BIT to Kconfig

This converts the following to Kconfig:
   CONFIG_NORFLASH_PS32BIT

Note that we also attempt to correct the behavior of the code here,
which had been testing for "NORFLASH_PS32BIT" which would never be set,
instead check for the now set "CONFIG_NORFLASH_PS32BIT", which results
in some behavior change.

Cc: TsiChung Liew <Tsi-Chung.Liew@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>