Don't truncate the input when decrypting in pkeyutl

The pkeyutl app was truncating the input file for decryption leading to
incorrect results. This was probably ok historically when RSA was being
used for decryption which has short maximum sizes. This is not ok with SM2.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from #21272)

(cherry picked from commit 8494507)

apps/lib/apps.c

@@ -2011,7 +2011,8 @@ int bio_to_mem(unsigned char **out, int maxlen, BIO *in)
             BIO_free(mem);
             return -1;
         }
-        maxlen -= len;
+        if (maxlen != -1)
+            maxlen -= len;
 
         if (maxlen == 0)
             break;

apps/pkeyutl.c

@@ -421,7 +421,7 @@ int pkeyutl_main(int argc, char **argv)
     /* Raw input data is handled elsewhere */
     if (in != NULL && !rawin) {
         /* Read the input data */
-        buf_inlen = bio_to_mem(&buf_in, keysize * 10, in);
+        buf_inlen = bio_to_mem(&buf_in, -1, in);
         if (buf_inlen < 0) {
             BIO_printf(bio_err, "Error reading input Data\n");
             goto end;