directfb: remove --program-prefix

--program-prefix is now set in the auto-target infrastructure.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/directfb/directfb.mk

@@ -12,7 +12,6 @@ DIRECTFB_INSTALL_STAGING = YES
 DIRECTFB_CONF_OPT = \
 	--localstatedir=/var \
 	--disable-explicit-deps \
-	--program-prefix='' \
 	--enable-zlib \
 	--enable-freetype \
 	--enable-fbdev \