MIPS: ath79: remove ar724x_pci_add_data function

The variables set by this function are not used anymore.
Remove the function and the relevant variables as well.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3501/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>