Break endless loop in serialport_write()

Serialport_write could loop endlessly when used with a seemingly valid port
that does always return 0 on writes instead of an error.
Give up after about 125 ms i.e. 250 tries with a period of 500 us.

Corresponding to flashrom svn r1626.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Idwer Vollering <vidwer@gmail.com>
1 file changed