qt5: bump version to 5.6.0

qt5: bump version to 5.6.0

Remove upstream committed patches (qt5base):
  - 0001-Force_egl_visual_ID_33.patch (see [1], [2])
  - 0003-xcb-egl-fixes.patch (see [3])
  - 0005-forkd-disable-eventfd-for-uclibc.patch (see [4], [5])
  - 0009-fix-eglfs-for-sunxi-mali.patch (see [6])
  - 0014-linux-oe-g-Invert-conditional-for-defining-QT_SOCKLE.patch (see [7])

Remove MX6_WORKAROUND from qt5base.mk since we do not need to tweak
EGL visual ID to 33.

Remove upstream committed patch (qt5webchannel):
  - 0001-Fix-builds-without-qml-module.patch (see [8], [9])

Fix Qt5Enginio to 1.6.0 version (see [10])

[1] https://bugreports.qt.io/browse/QTBUG-44290
[2] https://codereview.qt-project.org/#/c/108849/
[3] https://codereview.qt-project.org/#/c/115438/
[4] https://bugreports.qt.io/browse/QTBUG-47337
[5] https://codereview.qt-project.org/#/c/121988/
[6] https://codereview.qt-project.org/#/c/125837/
[7] https://codereview.qt-project.org/#/c/126725/
[8] https://bugreports.qt.io/browse/QTBUG-47360
[9] https://codereview.qt-project.org/#/c/122086/
[10] https://bugreports.qt.io/browse/QTBUG-50111

Signed-off-by: Julien Corjon <corjon.j@ecagroup.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>