irqdomain: Use return value of strreplace()

Since strreplace() returns the pointer to the string itself, use it
directly.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230628150251.17832-1-andriy.shevchenko@linux.intel.com