KVM: x86 emulator: Implement emulation of instruction: inc & dec

Instructions:
	inc r16/r32 (opcode 0x40-0x47)
	dec r16/r32 (opcode 0x48-0x4f)

Signed-off-by: Nitin A Kamble <nitin.a.kamble@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>