clk, reset: microchip: mpfs: fix incorrect preprocessor conditions

While moving all the reset code in the PolarFire SoC clock driver to the
reset subsystem, I removed an `#if IS_ENABLED(RESET_CONTROLLER)` from
the driver and moved it to the header, however this was not the correct
thing to do. In the driver such a condition over-eagerly provided a
complete implementation for mpfs_reset_{read,write}() when the reset
subsystem was enabled without the PolarFire SoC reset driver, but in the
header it meant that when the subsystem was enabled and the driver was
not, no implementation for mpfs_reset_controller_register() was
provided. Fix the condition so that the stub implementation of
mpfs_reset_controller_register() is used when the reset driver is
disabled.

Fixes: 098c290a

 ("clock, reset: microchip: move all mpfs reset code to the reset subsystem")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202405082259.44DzHvaN-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202405082200.tBrEs5CZ-lkp@intel.com/
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240508-unabashed-cheese-8f645b4f69ba@spud
Signed-off-by: Stephen Boyd <sboyd@kernel.org>