drivers: flash: add a generic spi nor flash driver

This driver is inspired from the w25qxxdv SPI NOR flash driver which was
already implementing the CFI (Common Flash Interface) for its purpose.
To handle other NOR flash a flash id table (as Linux do) which contains
the geometry for a few SPI NOR flash based on their JEDEC ID has been
introduced.
We currently support the following flash:
 - W25Q80
 - W25Q16
 - W25Q32
 - S25FL216K
 - MX25UM512

The read and write functions are able to handle more then one page at a
time and return the number of bytes read or write.
Also because every NOR flash expect to disable the write protection
before writing or erasing, the write enable command is now part of the
write and erase functions.

Signed-off-by: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
Signed-off-by: Savinay Dharmappa <savinay.dharmappa@intel.com>