devupstream.bbclass: Disable devupstream when multilib is enabled

devupstream.bbclass: Disable devupstream when multilib is enabled

Fixed:
MACHINE = "qemux86-64"
require conf/multilib.conf
MULTILIBS = "multilib:lib32"
DEFAULTTUNE_virtclass-multilib-lib32 = "x86"

PREFERRED_VERSION_lttng-modules = "2.10.10+git%"

$ bitbake world

NOTE: preferred version 2.10.10+git% of lttng-modules not available (for item lib32-lttng-modules)
NOTE: versions of lttng-modules available: 2.10.10
ERROR: Multiple versions of lttng-modules are due to be built (/path/to/lttng-modules_2.10.10.bb virtual:devupstream:target:/path/to/lttng-modules_2.10.10.bb). Only one version of a given PN should be built in any given build. You likely need to set PREFERRED_VERSION_lttng-modules to select the correct version or don't depend on multiple versions.

This is because 2.10.10+git% will be built for non-multilib lttng-modules since
the PREFERRED_VERSION is set, but this version doesn't provide
lib32-lttng-modules, so 2.10.10 will be built, then the error happens.

Bitbake can't extend an extended recipe, for example:
virtual:multilib:lib32:virtual:devupstream:target

Or in a reverse order:
virtual:devupstream:target:virtual:multilib:lib32

So disable devupstream when multilib is enabled.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>