linux-generic: makefile: fix distcheck failure
linux-generic: makefile: fix distcheck failure

Fixes https://bugs.linaro.org/show_bug.cgi?id=1813

make distcheck results in
../../../platform/linux-generic/include/odp_buffer_internal.h:33:33:
fatal error: odp_config_internal.h: No such file or director

Signed-off-by: Mike Holmes <ed44c09f4d7f698f5510adc894a872c73e08c8bd@linaro.org>
Reviewed-by: Bill Fischofer <52f3c909d51cc5d355a68a403df6906b3c1a8f83@linaro.org>
Signed-off-by: Maxim Uvarov <db4d16e02ae2d7493db430203537da8b2e34f290@linaro.org>

dkrot/odp,nmorey/odp,erachmi/odp,erachmi/odp,mike-holmes-linaro/odp,mike-holmes-linaro/odp,erachmi/odp,ravineet-singh/odp,ravineet-singh/odp,mike-holmes-linaro/odp,dkrot/odp,nmorey/odp,ravineet-singh/odp,erachmi/odp,mike-holmes-linaro/odp,ravineet-singh/odp,nmorey/odp,dkrot/odp,nmorey/odp,dkrot/odp