uru4000: Fix integer overflow in imaging_run_state()

‘img->key_number’ variable is originally from the device through bulk
endpoint of USB. The variable is immediately assigned to ‘buf[0]’ for
sending to control endpoint of the device. Here, integer overflow may
occur when the ‘img->key_number’ attempts to assign a value that is
outside of type range of ‘char’ to the ‘buf[0]’
2 jobs for master in 3 minutes and 10 seconds
latest
Status Job ID Name Coverage
  Build
passed #136751
build

00:01:07

 
  Test
passed #136752
flatpak master

00:02:02