brcm47xx: backport BCM47XX patches (NVRAM & BCMA_HOST_PCI)

...IPS-BCM47xx-Add-helper-variable-for-storing-NVRAM-l.patch

...3.18/032-10-MIPS-BCM47xx-Don-t-select-BCMA_HOST_PCI.patch

...cm47xx/patches-3.18/280-activate_ssb_support_in_usb.patch

...t/linux/brcm47xx/patches-3.18/820-wgt634u-nvram-fix.patch

target/linux/brcm47xx/patches-3.18/999-wl_exports.patch

...IPS-BCM47xx-Add-helper-variable-for-storing-NVRAM-l.patch

...-4.0/031-10-MIPS-BCM47xx-Don-t-select-BCMA_HOST_PCI.patch

...rcm47xx/patches-4.0/280-activate_ssb_support_in_usb.patch

...et/linux/brcm47xx/patches-4.0/820-wgt634u-nvram-fix.patch

target/linux/brcm47xx/patches-4.0/999-wl_exports.patch