MIPS: cpu-type: guard BMIPS variants with SYS_HAS_CPU_BMIPS*

BMIPS32 and  BMIPS3300 also need to be available for MIPS32R1, as
bcm47xx might not select BMIPS.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6245/