imx6: fix build error

This symbol is required when symbol SOC_IMX6 is also specified

Signed-off-by: Koen Vandeputte <[email protected]>

target/linux/generic/config-4.4

@@ -2791,6 +2791,7 @@ CONFIG_NLS_DEFAULT="iso8859-1"
 # CONFIG_NTP_PPS is not set
 # CONFIG_NVM is not set
 # CONFIG_NVMEM is not set
+# CONFIG_NVMEM_IMX_OCOTP is not set
 # CONFIG_NVRAM is not set
 # CONFIG_NV_TCO is not set
 # CONFIG_NXP_STB220 is not set