ACPI: APEI: EINJ: Remove redundant calls to einj_get_available_error_type()

A single call to einj_get_available_error_type() in init function is
sufficient to save the return value in a global variable to be used
later in various places in the code.

This change has no functional impact, but only removes unnecessary
redundant function calls.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Zaid Alali <zaidal@os.amperecomputing.com>
Link: https://patch.msgid.link/20250506213814.2365788-5-zaidal@os.amperecomputing.com


[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>