MIPS: ath25: add interrupts handling routines

Add interrupts initialization and handling routines, also add AHB bus
error interrupt handlers for both SoCs families.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Cc: Linux MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/8240/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --cc arch/mips/Kconfig
Simple merge

diff --cc arch/mips/ath25/ar2315.c
Simple merge

diff --cc arch/mips/ath25/ar2315.h
Simple merge

diff --cc arch/mips/ath25/ar2315_regs.h
Simple merge

diff --cc arch/mips/ath25/ar5312.c
Simple merge

diff --cc arch/mips/ath25/ar5312.h
Simple merge

diff --cc arch/mips/ath25/ar5312_regs.h
Simple merge

diff --cc arch/mips/ath25/board.c
Simple merge

diff --cc arch/mips/ath25/devices.h
Simple merge