iron out all extra compiler warnings

iron out all extra compiler warnings

gcc 9.1 on x86/64 has reported following:

 attr.c:403:19: error: comparison of integer expressions of different signedness: ‘int’ and ‘long unsigned int’ [-Werror=sign-compare]
 genl.c:154:24: error: comparison of integer expressions of different signedness: ‘int’ and ‘unsigned int’ [-Werror=sign-compare]
 genl_mngt.c:157:22: error: comparison of integer expressions of different signedness: ‘int’ and ‘long unsigned int’ [-Werror=sign-compare]
 msg.c:190:20: error: comparison of integer expressions of different signedness: ‘int’ and ‘long unsigned int’ [-Werror=sign-compare]
 msg.c:192:18: error: comparison of integer expressions of different signedness: ‘__u32’ {aka ‘const unsigned int’} and ‘int’ [-Werror=sign-compare]
 msg.c:361:10: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
 nl.c:428:18: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
 nl.c:602:23: error: comparison of integer expressions of different signedness: ‘__u32’ {aka ‘unsigned int’} and ‘int’ [-Werror=sign-compare]

Signed-off-by: Petr Štetiar <ynezz@true.cz>