[AVR32] Fix invalid status register bit definitions in asm/ptrace.h

The 'H' bit is bit 29, while the 'R' bit doesn't exist. Luckily, we
don't actually use any of the bits in question.

Also update show_regs() to show the Debug Mask and Debug state bits.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>