Fix type of "fp" and other registers for Nios II.

2014-03-25  Sandra Loosemore  <sandra@codesourcery.com>

	gdb/
	* features/nios2-cpu.xml: Correct types of "gp", "fp", "ea", and
	"ra" registers.
	* features/nios2-linux.c: Regenerated.
	* features/nios2.c: Regenerated.