AVR: Fix typo in device-specs generation. Reuse -m[no-]rodata-in-ram checker.

AVR: Fix typo in device-specs generation.  Reuse -m[no-]rodata-in-ram checker.

gcc/
	* config/avr/gen-avr-mmcu-specs.cc (diagnose_rodata_in_ram): Fix typo
	in the diagnostic, and capitalize the device name.
	(print_mcu): Generate specs such that:
	<*check_rodata_in_ram>: New.
	<*cc1_misc>: Use check_rodata_in_ram instead of cc1_rodata_in_ram.
	<*link_misc>: Use check_rodata_in_ram instead of link_rodata_in_ram.
	<*cc1_rodata_in_ram, *link_rodata_in_ram>: Remove.