fpga: zynqpl: fix buffer alignment

Due to pointer arithmetic, "sizeof(u32) * ARCH_DMA_MINALIGN" is
subtracted. It seems that the original intention was to just subtract
ARCH_DMA_MINALIGN. Fix it.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/drivers/fpga/zynqpl.c b/drivers/fpga/zynqpl.c
index a11e485..2de4010 100644
--- a/drivers/fpga/zynqpl.c
+++ b/drivers/fpga/zynqpl.c
@@ -315,7 +315,7 @@
 		if (new_buf > buf) {
 			debug("%s: Aligned buffer is after buffer start\n",
 			      __func__);
-			new_buf -= ARCH_DMA_MINALIGN;
+			new_buf = (u32 *)((u32)new_buf - ARCH_DMA_MINALIGN);
 		}
 		printf("%s: Align buffer at %x to %x(swap %d)\n", __func__,
 		       (u32)buf, (u32)new_buf, swap);