- Split one 4-byte R92C_CR register into 2-byte R92C_CR and 1-byte R92C_MSR
registers (they are used for different purposes).
- Wrap R92C_MSR modifications into urtwn_set_mode().
Reviewed by: kevlo
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D3838