serial: amba-pl011: Introduce set_uartclk_rate vendor flag

serial: amba-pl011: Introduce set_uartclk_rate vendor flag

The NVIDIA Tegra264 UART relies on configuring the UART clock rate
directly to program the desired baud rate.

Introduce the set_uartclk_rate vendor flag. When set, the driver
uses clk_set_rate() to program the UART clock to the desired baud
rate and clk_round_rate() to determine the maximum supported baud
rate.

Signed-off-by: Kartik Rajput <kkartik@nvidia.com>
Link: https://patch.msgid.link/20260225065915.341522-3-kkartik@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>