accel/ivpu: Refactor priority_bands_show for readability

accel/ivpu: Refactor priority_bands_show for readability

Reduce code duplication and improve the overall readability of the debugfs
output for job scheduling priority bands.

Additionally fix clang-tidy warning about missing default case in the
switch statement.

Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Signed-off-by: Karol Wachowski <karol.wachowski@linux.intel.com>
Link: https://lore.kernel.org/r/20250915103401.830045-1-karol.wachowski@linux.intel.com