mtd: spi-nor: copy the SPI NOR commands to a new header file

This patch adds a new header :spi-nor.h,
and copies all the SPI NOR commands and relative macros into this new header.

This hearder can be used by the m25p80.c and other spi-nor controller,
such as Freescale's Quadspi.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>