x86emul: simplify FPU source operand handling

x86emul: simplify FPU source operand handling

Consistently use ea instead of src for passing the memory address to
->read(). This eliminates the need to copy ea to src, resulting in a
couple of hundred bytes smaller binary size.

In addition for opcode DE we can leverage SrcMem16 to eliminate a call
of the ->read() hook. At the same time drop the stray Mov attributes
from D8, DA, DC, and DE: They're meaningful for memory writes only.

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