lttng-tools: Remove the scope resolution operator

lttng-tools: Remove the scope resolution operator

Remove the scope resolution operator :: to fix the below build failure.
 | ../../../sources/lttng-tools-2.14.0/src/common/eventfd.cpp:18:31: error: expected id-expression before numeric constant
 |    18 |                 int flags = ::EFD_CLOEXEC;
 |       |                               ^~~~~~~~~~~
 | ../../../sources/lttng-tools-2.14.0/src/common/eventfd.cpp:21:36: error: expected id-expression before numeric constant
 |    21 |                         flags |= ::EFD_SEMAPHORE;
 |       |

Signed-off-by: Mingli Yu <mingli.yu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>