tests: Add functional tests for ecb/cbc helpers

Test the following helper functions using AES with 128, 192, and
256 bit keys:
  - grub_crypto_ecb_encrypt(),
  - grub_crypto_ecb_decrypt(),
  - grub_crypto_cbc_encrypt(),
  - grub_crypto_cbc_decrypt().

Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
Reviewed-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Glenn Washburn <development@efficientek.com>

docs/grub.texi

@@ -4078,6 +4078,7 @@ Modules can be loaded via the @command{insmod} (@pxref{insmod}) command.
 * cpio_be_module::
 * cpuid_module::
 * crc64_module::
+* crypto_cipher_mode_test_module::
 * crypto_module::
 * cryptodisk_module::
 * cs5536_module::
@@ -4610,6 +4611,10 @@ various CPU features. @xref{cpuid} for more information.
 @section crc64
 This module provides support for the CRC64 operation.
 
+@node crypto_cipher_mode_test_module
+@section crypto_cipher_mode_test
+This module performs various cipher mode encryption/decryption tests
+
 @node crypto_module
 @section crypto
 This module provides library support for various base cryptography operations