pk: fix a return value and a typo in comment

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/pkparse.c b/library/pkparse.c
index d47b099..9bc8801 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -722,7 +722,7 @@
     } else {
         /* Uncompressed format */
         if ((end - *p) > MBEDTLS_PK_MAX_EC_PUBKEY_RAW_LEN) {
-            return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+            return MBEDTLS_ERR_PK_BUFFER_TOO_SMALL;
         }
         memcpy(pk->pub_raw, *p, (end - *p));
         pk->pub_raw_len = end - *p;