ANDROID: Fix warning for undeclared struct acr_info

The following warning is generated with CONFIG_CONTIG_ALLOC=n build:

include/trace/hooks/mm.h:54:25: warning: 'struct acr_info' declared inside parameter list will not be visible outside of this definition or declaration

Fix this by adding struct acr_info forward declaration.

Fixes: 45cb58e1 ("ANDROID: vendor_hooks: add vendor hoook to report acr_info in cma_alloc()")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I88f3f41e65f7239a8ab199bed27f33418566387d