[kernel] 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>
Patchwork: http://patchwork.openwrt.org/patch/3120/

git-svn-id: svn://svn.openwrt.org/openwrt@35361 3c298f89-4303-0410-b956-a3cf2f4a3e73