package: drop <PKG>_VERSION_MINOR variable

Since <PKG>_VARIABLE_MINOR variable in some packages is used only once,
so it is unusable. This patch removes it.

Signed-off-by: Jerzy Grzegorek <jerzy.grzegorek@trzebnica.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>