AVR: Rename device-specs %_misc to %_rodata_in_ram.

gcc/
	* config/avr/gen-avr-mmcu-specs.cc: Rename spec cc1_misc to
	cc1_rodata_in_ram.  Rename spec link_misc to link_rodata_in_ram.
	Remove spec asm_misc.
	* config/avr/specs.h: Same.