Fixed bug in disassembly of roundss/roundsd

Rationale:
These instructions should be marked as load, so that, using
Intel syntax, destination (xmm0) appears at left hand side, as in
   roundss xmm0, xmm1
and not the other way around. First I suspected a bug in the
encoding (hence the test) and even the register allocator, but
since the code behaved correctly, only disassembly was really wrong.

Test: disassembler_x86_test (but nothing for actual disassembly)

BUG=26327751

Change-Id: I060ef57f4d5a64cdc04b97ae8a799d1c0d22da05