KVM: x86 emulator: Stop passing ctxt->ops as arg of emul functions

Dereference it in the actual users.

This not only cleans up the emulator but also makes it easy to convert
the old emulation functions to the new em_xxx() form later.

Note: Remove some inline keywords to let the compiler decide inlining.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>