o Remove the com_thr, com_rhr, com_isr and com_lctl defines. They are

o  Remove the com_thr, com_rhr, com_isr and com_lctl defines. They are
   not used and aliases for other defines.
o  Add REG_DATA as an alias for com_data. Likewise for other register
   defines.
o  Add LCR_SBREAK and make CFCR_SBREAK an alias for it. Likewise for
   the other LCR register bits that are known with the CFCR prefix.
o  Add MCR_IE and make MCR_IENABLE an alias for it.
o  Add LSR_TEMT and make LSR_TSRE an alias for it.
o  Add LSR_THRE and make LSR_TXRDY as alias for it.
o  Add FCR_ENABLE and make FIFO_ENABLE as alias for it. Likewise for
   the other FCR register bits that are known with the FIFO prefix.
o  Add EFR_CTS and make EFR_AUTOCTS an alias for it.
o  Add EFR_RTS and make EFR_AUTORTS an alias for it.

This is a first step in cleaning up the definitions in this file.