tty: serial: qcom-geni-serial: Remove uart frequency table. Instead, find suitable frequency with call to clk_round_rate.

Replace the UART frequency table 'root_freq[]' with logic around
clk_round_rate() so that SoC details like the available clk frequencies
can change and this driver still works. This reduces tight coupling
between this UART driver and the SoC clk driver because we no longer
have to update the 'root_freq[]' array for new SoCs. Instead the driver
determines the available frequencies at runtime.
Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
Link: https://lore.kernel.org/r/1652697510-30543-1-git-send-email-quic_vnivarth@quicinc.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>