wifi: iwlwifi: dbg: use bit of DRAM alloc ID to store failed allocs

The failed_alloc variable is used as a bitmask in the loop where we
check DRAM allocations.  But erroneously, we were clearing the DRAM
alloc IDs we removed as an integer.

Fix that by clearing them as bits instead.

Signed-off-by: Rotem Saado <rotem.saado@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20221102165239.688dec28b1d9.I470b8d29c28d16f25f4192773f075940de7ed33c@changeid