util/spkmodem-recv: allow short sample reads

fread() may return short reads, whereas the current
code assumes either EOF or a full read.

change if to a while. really, it's that simple.
just loop until it's done. i probably b0rked this
myself when refactoring the GNU code.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/spkmodem_recv/spkmodem-recv.c

@@ -190,7 +190,7 @@ read_sample(struct decoder_state *st)
 {
 	size_t n;
 
-	if (st->inpos >= st->inlen) {
+	while (st->inpos >= st->inlen) {
 
 		n = fread(st->inbuf, sizeof(st->inbuf[0]),
 		    READ_BUF, stdin);