KVM: x86 emulator: Add mov r, imm instructions (opcodes 0xb0-0xbf)

The emulator only supported one instance of mov r, imm instruction
(opcode 0xb8), this adds the rest of these instructions.

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>