target-arm: Handle VMOV between two core and VFP single regs

Fix two bugs in the translation of the instructions VMOV sa,sb,rx,ry and
VMOV rx,ry,sa,sb (which copy between a pair of ARM core registers and a
pair of VFP single precision registers):

 * An incorrect condition meant these instruction patterns were being
   treated as load/store multiple, which resulted in the generation
   of bad code and a runtime segfault
 * The order of the core register pair was reversed so the values would
   go to the wrong registers

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>