package/bootutils: fix musl compilation issue

Fixes:
http://autobuild.buildroot.net/results/389/38914a0a7ff0aa79acbbbe6c46ab701325dfceb8/
http://autobuild.buildroot.net/results/c0d/c0d09f5dd0e26c0d2454ebb2ea5317db1135db89/



musl requires strict inclusion of <sys/types.h> for makedev(3).

note - upstream project appears dead since 2009.

Signed-off-by: Brendan Heading <brendanheading@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>