qca4019: qca9888: add bdfs for Netgear RBK20

All three boardfiles were extracted from this vendor image: RBR20-V2.7.5.6.img
Both RBR20 and RBS20 use the same boardfiles.

board-netgear_rbk20.qca4019:
FileSize: 24316
FileCRC32: d4b46c1d
FileMD5: 53c8e9070eb73da8d57d26acb2b63341
BoardNames[0]: 'bus=ahb,bmi-chip-id=0,bmi-board-id=20,variant=Netgear-RBK20'
BoardLength[0]: 12064
BoardCRC32[0]: b237383e
BoardMD5[0]: ad1e2924e64ee8c9f8756dd511a161c6
BoardNames[1]: 'bus=ahb,bmi-chip-id=0,bmi-board-id=21,variant=Netgear-RBK20'
BoardLength[1]: 12064
BoardCRC32[1]: 7f1e595c
BoardMD5[1]: db9b2aafa442140e7327020cfa98f09b

board-netgear_rbk20.qca9888:
FileSize: 12168
FileCRC32: 48cfa8e5
FileMD5: 7d9cd8f847dac8150b5f7c38cfdf02a7
BoardNames[0]: 'bus=pci,bmi-chip-id=0,bmi-board-id=17,variant=Netgear-RBK20'
BoardLength[0]: 12064
BoardCRC32[0]: d28bd550
BoardMD5[0]: ef84f0eba6035c5f4233d1c52f3d4d0e

Signed-off-by: Christoph Krapp <achterin@gmail.com>
Link: #113
Signed-off-by: Robert Marko <robimarko@gmail.com>

Author: achterin