devres: restore zeroing behavior of devres_alloc()

commit 64c862a8 (devres: add kernel standard devm_k.alloc functions) changed
the default behavior of alloc_dr() to no longer zero the allocated memory.  However,
only the devm.k.alloc() function were modified to pass in __GFP_ZERO which leaves
any users of devres_alloc() or __devres_alloc() with potentially wrong assumptions
about memory being zero'd upon allocation.

To fix, add __GFP_ZERO to devres_alloc() calls to preserve previous
behavior of zero'ing memory upon allocation.

Signed-off-by: Kevin Hilman <khilman@linaro.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>