rsa: simplify mbedtls_rsa_parse_pubkey() input parameters

In this way mbedtls_rsa_parse_pubkey() and mbedtls_rsa_parse_key()
input parameter list is the same.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/psa_crypto_rsa.c b/library/psa_crypto_rsa.c
index 0047a26..4a574d1 100644
--- a/library/psa_crypto_rsa.c
+++ b/library/psa_crypto_rsa.c
@@ -73,9 +73,7 @@
     if (PSA_KEY_TYPE_IS_KEY_PAIR(type)) {
         status = mbedtls_to_psa_error(mbedtls_rsa_parse_key(*p_rsa, data, data_length));
     } else {
-        unsigned char *p = data;
-        unsigned char *end = (data + data_length);
-        status = mbedtls_to_psa_error(mbedtls_rsa_parse_pubkey(*p_rsa, &p, end));
+        status = mbedtls_to_psa_error(mbedtls_rsa_parse_pubkey(*p_rsa, data, data_length));
     }
     if (status != PSA_SUCCESS) {
         goto exit;