fscrypt-crypt-util: clean up parsing --block-size and --inode-number

fscrypt-crypt-util: clean up parsing --block-size and --inode-number

For --block-size, check for strtoul() reporting an overflow.

For --inode-number, check for strtoull() reporting an overflow.

Also, move the check for 32-bit inode numbers into a more logical place
(the place where we check the encryption format-specific limitations).

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Daeho Jeong <daeho43@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>