qt5/qt5base: Fix build on big endian systems

Backporting an upstream patch to fix a qt5base build failure on big
endian systems. This is the error message:

image/qimage_conversions.cpp:2257:9: error: expected '}' before numeric
constant

Upstream commit:

  https://qt.gitorious.org/qt/qtbase/commit/404f4281fda764cafdaa5635db995dabc4f1de8c



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>