Fix spelling and typographical errors found by cspell

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 6acd9b1..1cd6eb6 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -2918,7 +2918,7 @@
  *
  * Requires: MBEDTLS_MD_C
  *
- * Uncomment to enable the HMAC_DRBG random number geerator.
+ * Uncomment to enable the HMAC_DRBG random number generator.
  */
 #define MBEDTLS_HMAC_DRBG_C