KVM: nVMX: VMX instructions: add checks for #GP/#SS exceptions

According to Intel SDM several checks must be applied for memory operands
of VMX instructions.

Long mode: #GP(0) or #SS(0) depending on the segment must be thrown
if the memory address is in a non-canonical form.

Protected mode, checks in chronological order:
- The segment type must be checked with access type (read or write) taken
into account.
	For write access: #GP(0) must be generated if the destination operand
		is located in a read-only data segment or any code segment.
	For read access: #GP(0) must be generated if if the source operand is
		located in an execute-only code segment.
- Usability of the segment must be checked. #GP(0) or #SS(0) depending on the
	segment must be thrown if the segment is unusable.
- Limit check. #GP(0) or #SS(0) depending on the segment must be
	thrown if the memory operand effective address is outside the segment
	limit.

Signed-off-by: Eugene Korenevsky <ekorenevsky@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>