ARM: mx5: Set the DBGEN bit in ARM_GPC register

On i.MX51/i.MX53 it is necessary to set the DBGEN bit in
ARM_GPC register in order to turn on the debug clocks.

The DBGEN bit of ARM_GPC register has the following description
in the i.MX53 Reference Manual:

"This allows the user to manually activate clocks within the debug
system. This register bit directly controls the platform's dbgen_out
output signal which connects to the DAP_SYS to enable all debug clocks.
Once enabled, the clocks cannot be disabled except by asserting the
disable_trace input of the DAP_SYS."

Based on a previous patch from Sebastian Reichel.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/mach-imx/mach-imx51.c

@@ -80,6 +80,7 @@ static void __init imx51_dt_init(void)
 	imx51_ipu_mipi_setup();
 	imx_src_init();
 	imx51_m4if_setup();
+	imx5_pmu_init();
 	imx_aips_allow_unprivileged_access("fsl,imx51-aipstz");
 }