crypto: iaa - Fix out-of-bounds index in find_empty_iaa_compression_mode

crypto: iaa - Fix out-of-bounds index in find_empty_iaa_compression_mode

The local variable 'i' is initialized with -EINVAL, but the for loop
immediately overwrites it and -EINVAL is never returned.

If no empty compression mode can be found, the function would return the
out-of-bounds index IAA_COMP_MODES_MAX, which would cause an invalid
array access in add_iaa_compression_mode().

Fix both issues by returning either a valid index or -EINVAL.

Cc: stable@vger.kernel.org
Fixes: b190447e0fa3 ("crypto: iaa - Add compression mode management along with fixed mode")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Acked-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>