i3c: mipi-i3c-hci: Factor out software reset into helper

i3c: mipi-i3c-hci: Factor out software reset into helper

Prepare for future reuse of the reset sequence in other contexts, such as
power management.  Move the software reset logic from i3c_hci_init() into a
dedicated helper function, i3c_hci_software_reset().

Software reset should never fail.  Print an error message if it does.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260113072702.16268-15-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>