i2c: riic: Use dev_err_probe in probe and riic_init_hw functions

Refactor error handling in the riic_i2c_probe() and riic_init_hw()
functions by replacing multiple dev_err() calls with dev_err_probe().

Additionally, update the riic_init_hw() function to use a local `dev`
pointer instead of `riic->adapter.dev` for dev_err_probe(), as the I2C
adapter is not initialized at this stage. Drop the cast to (unsigned long)
in the riic_init_hw() function when printing the bus frequency, and update
the error message to display the frequency in Hz, improving clarity.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>