mtd: chips: Add support for GigaDevice GD25Q32/GD25Q64 SPI Flash in m25p80.c

Add support for GigaDevice GD25Q32 32 Mbit (4 MB) SPI Flash (see datasheet:
http://www.gigadevice.com/UserFiles/GD25Q32_Rev0.2(1).pdf) used in Hame MPR-A1
and clones, and for GigaDevice GD25Q64 64 Mbit (8 MB) SPI Flash used in
Hame MPR-A2 devices (datasheet: http://www.gigadevice.com/UserFiles/GD25Q64.pdf

).

Signed-off-by: Michel Stempin <michel.stempin@wanadoo.fr>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>