Remove the SMP code from locore-v4. These will never use the SMP code as
there is no multi-core hardware prior to ARMv6.

Remove the armv6 code from locore-v4.S, it's not needed there.

Fix the style of locore-v4.S and locore-v6.S to help find any common code.

Cleanup a little more:
 - Remove whitespace at the end of lines
 - Use a tab after instructions, not spaces

Fix the spelling of __ARM_ARCH >= 6 in sys/arm/arm.