KVM: x86 emulator: move all x86_emulate_memop() to a structure

Move all x86_emulate_memop() common variables between decode and execute to a
structure decode_cache.  This will help in later separating decode and
emulate.

            struct decode_cache {
                u8 twobyte;
                u8 b;
                u8 lock_prefix;
                u8 rep_prefix;
                u8 op_bytes;
                u8 ad_bytes;
                struct operand src;
                struct operand dst;
                unsigned long *override_base;
                unsigned int d;
                unsigned long regs[NR_VCPU_REGS];
                unsigned long eip;
                /* modrm */
                u8 modrm;
                u8 modrm_mod;
                u8 modrm_reg;
                u8 modrm_rm;
                u8 use_modrm_ea;
                unsigned long modrm_ea;
                unsigned long modrm_val;
           };

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>