The first argument of test_bit() and clear_bit() is a bit number and
not a bitmask. Hence change that first argument from (1 << 0) into 0.
This patch avoids that smatch reports the following warnings:

user_sdma.c:1059: sdma_cache_evict() warn: test_bit() takes a bit number
user_sdma.c:1590: sdma_rb_remove() warn: test_bit() takes a bit number
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>