utils: spkmodem: suggest to use parec instead of parecord

Using recent versions of parecord produces the following:
Failed to open audio file.

According to the manual:
  -r | --record
         Capture audio data and write it to the specified file or to STDOUT if none is specified. If the
         tool is called under the name parec this is the default.

so we suggest parec instead.

Change-Id: I8b821df67b10e9d6533c4cbe19c646c84d436c27
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
Reviewed-on: https://review.coreboot.org/23863
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Kocialkowski <contact@paulk.fr>

util/spkmodem_recv/spkmodem-recv.c

@@ -18,7 +18,7 @@
 #include <string.h>
 
 /* Compilation:  gcc -o spkmodem-recv spkmodem-recv  */
-/* Usage: parecord --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv */
+/* Usage: parec --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv */
 
 #define SAMPLES_PER_TRAME 240
 #define FREQ_SEP_MIN 5