system_info: Fix coding style violations.

system_info: Fix coding style violations.

./system_info/system_info_sim_ivi.cc:129:  If an else has a brace on one side, it should have it on both  [readability/braces] [5]
./system_info/system_info_locale.h:35:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_cellular_network.h:34:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_network.h:54:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_wifi_network.h:44:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_cpu.h:37:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_device_orientation.h:41:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_peripheral.h:34:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_battery.h:38:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_build.h:44:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]
./system_info/system_info_display.h:48:  Zero-parameter constructors should not be marked explicit.  [runtime/explicit] [5]

BUG=XWALK-2649