mtd: spi: Add flash property for Micron mt25qu512a

mt25qu512a is rebranded after its spinoff from STM, so it is
different only in term of extended jedec ID, initial JEDEC id
is same as that of n25q512a.In order to avoid any confussion
with respect to name new entry is added.

This flash is tested for Single I/O mode on LS1046FRWY although
it also support QUAD I/O.

Signed-off-by: Ashish Kumar <Ashish.Kumar@nxp.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>