arm: unify reset command

cpu/arm1136/cpu.c

cpu/arm1176/cpu.c

cpu/arm720t/cpu.c

cpu/arm920t/cpu.c

cpu/arm925t/cpu.c

cpu/arm926ejs/cpu.c

cpu/arm946es/cpu.c

cpu/arm_cortexa8/cpu.c

cpu/arm_intcm/cpu.c

cpu/ixp/cpu.c

cpu/lh7a40x/cpu.c

cpu/pxa/cpu.c

cpu/s3c44b0/cpu.c

cpu/sa1100/cpu.c

lib_arm/Makefile

lib_arm/reset.c