brcm47xx: mtd: bcm47xxpart: detect "factory" partition

A new type of partition with magic FCTY was found on Huawei E970:
46 43 54 59 4b 51 37 4e  41 42 31 38 41 32 39 30  |FCTYKQ7NAB18A290|

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

SVN-Revision: 38005