ARM: i.MX6: exclude the ARM errata from i.MX6 UP system

The ARM errata 751472, 794072, 761320 only applied
to the following configuration:

This erratum affects configurations with either:
- One processor if the ACP is present
- Two or more processors

i.MX6 family does not have the ACP and thus only the MPCore system
will be impacted, which are the i.MX6DQ, i.MX6DL, and i.MX6QP.
Signed-off-by: NPeng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>

arch/arm/mach-imx/mx6/Kconfig

 if ARCH_MX6
 
+config MX6_SMP
+	select ARM_ERRATA_751472
+	select ARM_ERRATA_761320
+	select ARM_ERRATA_794072
+	bool
+
 config MX6
+	select ARM_ERRATA_743622 if !MX6UL
 	bool
 	default y
-	select ARM_ERRATA_743622 if !MX6UL
-	select ARM_ERRATA_751472 if !MX6UL
-	select ARM_ERRATA_761320 if !MX6UL
-	select ARM_ERRATA_794072 if !MX6UL
 	imply CMD_FUSE
 
 config MX6D
+	select MX6_SMP
 	bool
 
 config MX6DL
+	select MX6_SMP
 	bool
 
 config MX6Q
+	select MX6_SMP
 	bool
 
 config MX6QDL
+	select MX6_SMP
 	bool
 
 config MX6S