package/pinentry: avoid building qt5 version if qt4 is enabled

BR2_PACKAGE_PINENTRY_QT5 selects BR2_PACKAGE_QT5, which can lead to Qt
version clash if otherwise Qt4 is selected as well. Making
BR2_PACKAGE_PINENTRY_QT5 depending on !BR2_PACKAGE_QT to avoid this.

Fixes:
     http://autobuild.buildroot.net/results/3c537e1260dc9ce57657ca0d49e318a10aee111e



Signed-off-by: Zoltan Gyarmati <mr.zoltan.gyarmati@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>