ima: Fix memory leak in __ima_inode_hash()

In the Linux kernel, the following vulnerability has been resolved:

ima: Fix memory leak in __ima_inode_hash()

Commit f3cc6b25dcc5 ("ima: always measure and audit files in policy") lets

measurement or audit happen even if the file digest cannot be calculated.

As a result, iint->ima_hash could have been allocated despite

ima_collect_measurement() returning an error.

Since ima_hash belongs to a temporary inode metadata structure, declared

at the beginning of __ima_inode_hash(), just add a kfree() call if

ima_collect_measurement() returns an error different from -ENOMEM (in that

case, ima_hash should not have been allocated).