Revert r496041 and r496054.

The changes were right, but they broke `make configure' in ports that have
USE_KDE=wayland because now both Mk/Uses/qt.mk and Mk/Uses/kde.mk set
wayland_PORT and wayland_LIB, and qt.mk's version overrides kde.mk's. This
means we will end up installing graphics/qt5-wayland rather than
x11/kf5-kwayland:

CMake Error at CMakeLists.txt:27 (find_package):

Could not find a package configuration file provided by "KF5Wayland"
(requested version 5.54.0) with any of the following names:

  KF5WaylandConfig.cmake
  kf5wayland-config.cmake

Add the installation prefix of "KF5Wayland" to CMAKE_PREFIX_PATH or set
"KF5Wayland_DIR" to a directory containing one of the above files.  If
"KF5Wayland" provides a separate development package or SDK, be sure it has
been installed.

Bump PORTREVISION in x11/kf5-plasma-framework, it has an optional dependency on
kf5-kwayland and was thus building fine despite the wrong dependencies.