migration/i386: Remove old non-softfloat 64bit FP support

migration/i386: Remove old non-softfloat 64bit FP support

Long long ago, we used to support storing the x86 FP registers in
a 64bit format.

Then c31da136a0bf8caad70c348f5ffc283206e9c7fc in v0.14-rc0 removed
the last support for writing that in the migration format.
Even before that, it was only used if you had softfloat disabled
 (i.e. !USE_X86LDOUBLE) so in practice use of it in even earlier
qemu is unlikely for most users.

Kill it off, it's complicated, and possibly broken.

Signed-off-by: Dr. David Alan Gilbert <[email protected]>
Message-Id: <20170405190024[email protected]>
Reviewed-by: Juan Quintela <[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>