Add support to ratified B Standard Extension for Bit Manip. Instructions

Created by: xiaoweish

Add support to B Standard Extension for Bit Manipulation Instructions listed in Ratified Extensions.

Chapter 1. B Standard Extension for Bit Manipulation Instructions The B standard extension comprises instructions provided by the Zba, Zbb, and Zbs extensions. 1.1. Privileged Architecture Implications Bit 1 of the misa register encodes the presence of the B standard extension. When misa.B is 1, the implementation supports the instructions provided by the Zba, Zbb, and Zbs extensions. When misa.B is 0, it indicates that the implementation may not support one or more of the Zba, Zbb, or Zbs extensions.