image/populate_sdk.bbclass: drop qemuwrapper-cross from DEPENDS

image/populate_sdk.bbclass: drop qemuwrapper-cross from DEPENDS

For packages that need qemuwrapper-cross, they should have it
in PAKAGE_WRITE_DEPS.

Now that we've used 'qemuwrapper-cross' to replace 'qemu-native'
for recipes that need qemu-native for their postinsts, and we've
now mapped PACKAGE_WRITE_DEPS for nativesdk recipes, these
qemuwrapper-cross dependencies can be dropped from image.bbclass
and populate_sdk.bbclass.

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>