ep93xx: clock: convert in-place to COMMON_CLK

Converted in-place without moving file to drivers/clk.

tested on ts7250 (EP9302).

Only setting rate and change parent tested for, as they
are missing on ts7250:
- video
- I2S
- ADC/KEYPAD
- PWM

Only video and I2S clock are interesting, as they are
GATE + double DIV + MUX, all other are pretty much
common but require ep93xx_syscon_swlocked_write to set
registers.

Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Tested-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Link: https://lore.kernel.org/r/20211018103105.146380-3-alexander.sverdlin@gmail.com

'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>