The former SH/SCIF driver had calculated baudrate based on CONFIG_SYS_CLK_FREQ.
The newest SH/SCIF needs calculation of the clock for SCIF.
This patch defines clock CONFIG_SH_SCIF_CLK_FREQ for SCIF and changes it to
CONFIG_SH_SCIF_CLK_FREQ from CONFIG_SYS_CLK_FREQ.