imx6: cache: disable L2 before touching Auxiliary Control Register

According PL310 TRM, Auxiliary Control Register
"
The register must be written to using a secure access, and it can be
read using either a secure or a NS access. If you write to this register
with a NS access, it results in a write response with a DECERR response,
and the register is not updated. Writing to this register with the L2
cache enabled, that is, bit[0] of L2 Control Register set to 1,
results in a SLVERR.
"

So If L2 cache is already enabled by ROM, chaning value of ACR
will cause SLVERR and uboot hang.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>

arch/arm/imx-common/cache.c

@@ -42,6 +42,12 @@ void v7_outer_cache_enable(void)
 	unsigned int val;
 
 
+	/*
+	 * Must disable the L2 before changing the latency parameters
+	 * and auxiliary control register.
+	 */
+	clrbits_le32(&pl310->pl310_ctrl, L2X0_CTRL_EN);
+
 	/*
 	 * Set bit 22 in the auxiliary control register. If this bit
 	 * is cleared, PL310 treats Normal Shared Non-cacheable
@@ -59,9 +65,6 @@ void v7_outer_cache_enable(void)
 	}
 #endif
 
-	/* Must disable the L2 before changing the latency parameters */
-	clrbits_le32(&pl310->pl310_ctrl, L2X0_CTRL_EN);
-
 	writel(0x132, &pl310->pl310_tag_latency_ctrl);
 	writel(0x132, &pl310->pl310_data_latency_ctrl);