If major equals 0, register_chrdev() returns an error code when it fails.
This function dynamically allocates a major and returns its number on
success, so we should use "< 0" to check it instead of "!".

Link: https://lore.kernel.org/r/20220418105755.2558828-1-lv.ruyi@zte.com.cnReported-by: NZeal Robot <zealci@zte.com.cn>
Signed-off-by: NLv Ruyi <lv.ruyi@zte.com.cn>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>