core_panic() doesn't expect the message to be in program memory, but
in data memory. Bad things will happen on AVR when the address is
interpreted as being in data address space, but the allocation is
done in program address space.
Split cpu.c file into cpu.c and atmega_cpu.c files. This extract mega
specific code from common code.
Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
