MIPS: Add BMIPS processor types to Kconfig

[v2: add "VIPER" marketing name for BMIPS4350]

Add processor feature definitions for BMIPS3300, BMIPS4350, BMIPS4380,
and BMIPS5000.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Cc: mbizon@freebox.fr
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Tested-by: Florian Fainelli <ffainelli@freebox.fr>
Patchwork: https://patchwork.linux-mips.org/patch/1716/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>