firmware: raspberrypi: Define timeout for transactions

firmware: raspberrypi: Define timeout for transactions

We should never assume to get a reply from the firmware otherwise
the call could block forever and the user don't get informed. So
define a timeout of 1 sec and print a stacktrace once in the unlikely
case the timeout expired.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
[jhoon20.kim: cherry picked from commit 0829187b17d8 for debugging booting issues]
Signed-off-by: Junghoon Kim <jhoon20.kim@samsung.com>
Change-Id: I2bb14167174662a84c6b2a8caaffc70485693816