package/openipmi: fix musl build

The build error is known upstream
http://sourceforge.net/p/openipmi/patches/26/


and was not yet caught by our autobuilders:

ui.c: In function ‘get_ip_addr’:
ui.c:340:5: error: unknown type name ‘u_int32_t’
     u_int32_t     addr;

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>