rules.mk: remove GCC 4.4 and GCC 4.5 conditional

gcc 4.4 was removed in r44957 gcc: remove 4.4.7 (only used by avr32)
gcc 4.5 was removed in r36149

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46722 3c298f89-4303-0410-b956-a3cf2f4a3e73