mtd: m25p80: use the SPI nor framework

Use the new SPI nor framework, and rewrite the m25p80:
 (0) remove all the NOR comands.
 (1) change the m25p->command to an array.
 (2) implement the necessary hooks, such as m25p80_read/m25p80_write.

Tested with the m25p32.
Signed-off-by: Huang Shijie <b32955@freescale.com>
Acked-by: Marek Vasut <marex@denx.de>
[Brian: rebased]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>