drivers: i2c: mxc: Fix compiler error when using i2c dm mode

I2C dm mode enablemenet causes below compilation errors:

In file included from include/config.h:8:0,
                 from include/common.h:20:
include/config_fallbacks.h:51:4: error: #error "Cannot define
CONFIG_SYS_I2C when CONFIG_DM_I2C is used"
 #  error "Cannot define CONFIG_SYS_I2C when CONFIG_DM_I2C is used"
    ^~~~~
In file included from include/config.h:8:0,
                 from include/common.h:20:
include/config_fallbacks.h:51:4: error: #error "Cannot define
CONFIG_SYS_I2C when CONFIG_DM_I2C is used"
 #  error "Cannot define CONFIG_SYS_I2C when CONFIG_DM_I2C is used"
    ^~~~~

board/freescale/lx2160a/lx2160a.c: In function 'board_early_init_f':
board/freescale/lx2160a/lx2160a.c:108:2: warning: implicit declaration
of function 'i2c_early_init_f'; did you mean 'arch_early_init_r'?
[-Wimplicit-function-declaration]
  i2c_early_init_f();
  ^~~~~~~~~~~~~~~~
  arch_early_init_r

 drivers/i2c/mxc_i2c.c: In function 'mxc_i2c_probe':
  drivers/i2c/mxc_i2c.c:824:8: warning: implicit declaration of function
'enable_i2c_clk';
  did you mean 'enable_irq_wake'? [-Wimplicit-function-declaration]
  ret = enable_i2c_clk(1, bus->seq);
        ^~~~~~~~~~~~~~
        enable_irq_wake

So fix these compilation errors.

Signed-off-by: Chuanhua Han <chuanhua.han@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/arch/arm/include/asm/arch-fsl-layerscape/config.h b/arch/arm/include/asm/arch-fsl-layerscape/config.h
index eb21c09..a83c70e 100644
--- a/arch/arm/include/asm/arch-fsl-layerscape/config.h
+++ b/arch/arm/include/asm/arch-fsl-layerscape/config.h
@@ -178,8 +178,10 @@
 #elif defined(CONFIG_ARCH_LX2160A)
 #define TZPC_BASE				0x02200000
 #define TZPCDECPROT_0_SET_BASE			(TZPC_BASE + 0x804)
+#if !defined(CONFIG_DM_I2C)
 #define CONFIG_SYS_I2C
 #define CONFIG_SYS_I2C_EARLY_INIT
+#endif
 #define SRDS_MAX_LANES  8
 #ifndef L1_CACHE_BYTES
 #define L1_CACHE_SHIFT		6