crypto: essiv - fix AEAD capitalization and preposition use in help text

"AEAD" is capitalized everywhere else.
Use "an" when followed by a written or spoken vowel.

Fixes: be1eb7f7 ("crypto: essiv - create wrapper template for ESSIV generation")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -511,10 +511,10 @@ config CRYPTO_ESSIV
 	  encryption.
 
 	  This driver implements a crypto API template that can be
-	  instantiated either as a skcipher or as a aead (depending on the
+	  instantiated either as an skcipher or as an AEAD (depending on the
 	  type of the first template argument), and which defers encryption
 	  and decryption requests to the encapsulated cipher after applying
-	  ESSIV to the input IV. Note that in the aead case, it is assumed
+	  ESSIV to the input IV. Note that in the AEAD case, it is assumed
 	  that the keys are presented in the same format used by the authenc
 	  template, and that the IV appears at the end of the authenticated
 	  associated data (AAD) region (which is how dm-crypt uses it.)