configure.ac: remove unused dynamic linkage flag
configure.ac: remove unused dynamic linkage flag

configure.ac defines a SPICEC_STATIC_LINKAGE_BDYNAMIC variable
when --enable-static-linkage is not set, but it's never used.
SPICEC_STATIC_LINKAGE_BSTATIC is used in client/, but since we
are using libtool, it might be more appropriate to use
'make LDFLAGS="-all-static"' to achieve static link.

elmarco/spice,Fantu/spice,elmarco/spice,mathslinux/spice,Fantu/spice,dezelin/spice,alon/spice-server,fgouget/spice,Fantu/spice,SPICE/spice,fgouget/spice,elmarco/spice,mathslinux/spice,mathslinux/spice,dezelin/spice,alon/spice-server,alon/spice-server,freedesktop-unofficial-mirror/spice__spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,elmarco/spice,SPICE/spice,mathslinux/spice,ya-mouse/spice,dezelin/spice,fgouget/spice,alon/spice-server,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,elmarco/spice,mathslinux/spice,dezelin/spice,alon/spice-server,fgouget/spice,freedesktop-unofficial-mirror/spice__spice,freedesktop-unofficial-mirror/spice__spice,ya-mouse/spice,dezelin/spice,ya-mouse/spice