ACPI: APEI: EINJ: Refactor available_error_type_show()

Move error type descriptions into an array and loop over error types
to improve readability and maintainability.

Replace seq_printf() with seq_puts() as recommended by checkpatch.pl.

Signed-off-by: Jay Lu <jaylu102@amd.com>
Co-developed-by: Ben Cheatham <benjamin.cheatham@amd.com>
Signed-off-by: Ben Cheatham <benjamin.cheatham@amd.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>