irqdomain: Remove stray '-' in the domain name

When the domain suffix is not supplied alloc_fwnode_name() unconditionally
adds a separator.

Fix the format strings to get rid of the stray '-' separator.

Fixes: 1e7c0529 ("irqdomain: Allow giving name suffix for domain")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240812193101.1266625-3-andriy.shevchenko@linux.intel.com