i3c: renesas: Factor out hardware initialization to separate function

i3c: renesas: Factor out hardware initialization to separate function

Move the hardware initialization sequence in renesas_i3c_bus_init()
into a dedicated renesas_i3c_hw_init() helper.

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/795327270a6ceb23e15513a2619a19ae4876cfba.1767781092.git.tommaso.merciai.xr@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>