x86emul: extend x86_insn_is_mem_write() coverage

x86emul: extend x86_insn_is_mem_write() coverage

Several insns were missed when this function was first added. As far as
insns already supported by the emulator go - SMSW and {,V}STMXCSR were
wrongly considered r/o insns so far.

Insns like the VMX, SVM, or CET-SS ones, PTWRITE, or AMD's new SNP ones
are intentionally not covered just yet. VMPTRST is put there just to
complete the respective group.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>