softfloat: fix for C99

C99 appears to consider compound literals as non-constants, and complains
when they are used in static initializers.  Switch to ordinary initializer
syntax.

Signed-off-by: Avi Kivity <avi@redhat.com>
Acked-by: Andreas Färber <afaerber@suse.de>
Reported-by: Andreas Färber <andreas.faerber@web.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
