firmware-utils: mksercommfw: fix compiler warnings/errors
mksercommfw.c:134:56: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
string_fortified.h:106:10: error: ‘__builtin_strncpy’ output truncated before terminating nul copying 7 bytes from a string of the same length [-Werror=stringop-truncation]
string_fortified.h:106:10: error: ‘__builtin_strncpy’ output truncated before terminating nul copying 7 bytes from a string of the same length [-Werror=stringop-truncation]
Signed-off-by: Petr Štetiar <ynezz@true.cz>