MIPS: JZ4750D: Use SYS_SUPPORTS_ZBOOT
defconfig: JZ4750D: Use SYS_SUPPORTS_ZBOOT
MIPS: JZ4750D: Remove unused IRQ_DOMAIN switch
MIPS: JZ4750: Small cleanup in time.c
MIPS: JZ4750D: Enable audio device for Ritmix RZX-50
deconfig: Update Ritmix RZX-50 config for kernel 3.15