i3c: renesas: Store clock rate and reset controls in struct renesas_i3c

i3c: renesas: Store clock rate and reset controls in struct renesas_i3c

Update the struct renesas_i3c to store the clock rate, presetn and
tresetn handlers. Replace local usage of the clock rate and reset
controls with these structure fields.

Simplify the code and prepare the driver for upcoming suspend/resume
support.

No functional change intended.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://patch.msgid.link/9e1da95dd9137590c752ecd9429925afcbeb918b.1767781092.git.tommaso.merciai.xr@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>