The variable 'data' is assigned null and never re-assigned. There
is also a redundant check for data being non-null which is always
false, so remove this and the variable data and dma_addr as they
are not used once the dead code has been removed.

Detected with CoverityScan, CID#1324015 ("'Constant' variable gaurds
dead code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Jie Yang <yang.jie@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>