clk: sunxi-ng: sun5i: Fix ahb_bist_clk definition

AHB BIST gate is actually controlled with bit 7.

This bug was detected while trying to use the NAND controller which is
using the DMA engine to transfer data to the NAND.
Since the ahb_bist_clk gate bit conflicts with the ahb_dma_clk gate bit,
the core was disabling the DMA engine clock as part of its 'disable
unused clks' procedure, which was causing all DMA transfers to fail after
this point.

Fixes: 5e737617 ("clk: sunxi-ng: Add sun5i CCU driver")
Cc: stable@vger.kernel.org
Reported-by: Angus Ainslie <angus@akkea.ca>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Angus Ainslie <angus@akkea.ca>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1495643669-28221-1-git-send-email-boris.brezillon@free-electrons.com