drivers: memc: stm32: add support for st,mem-swap

Implements H7 FMC binding memory remap
or swap configuration.

Enables:
* sdram-sram - swaps the NOR/PSRAM and SDRAM banks.
* sdramb2 - remaps SDRAM bank 2.

Does nothing for 'disabled' value (default mapping, reset state).

Signed-off-by: Georgij Cernysiov <geo.cgv@gmail.com>