ACPI: AGDI: fix missing newline in error message

ACPI: AGDI: fix missing newline in error message

Add the missing trailing newline to the dev_err() message
printed when SDEI event registration fails.

This keeps the error output as a properly terminated log line.

Fixes: a2a591fb76e6 ("ACPI: AGDI: Add driver for Arm Generic Diagnostic Dump and Reset device")
Reviewed-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Signed-off-by: Haoyu Lu <hechushiguitu666@gmail.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>