mpc83xx: Add arch clock.h to make SDHC work

The fsl-esdhc driver can be used for the SDHC functionality on MPC83xx,
but it needs some additional definitions.

Add a clock.h file, so we can use the driver for MPC83xx.

Signed-off-by: Mario Six <mario.six@gdsys.cc>

arch/powerpc/include/asm/arch-mpc83xx/clock.h

@@ -0,0 +1,22 @@
+/*
+ * (C) Copyright 2018
+ * Mario Six, Guntermann & Drunck GmbH, mario.six@gdsys.cc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __ASM_POWERPC_CLOCK_H
+#define __ASM_POWERPC_CLOCK_H
+
+/* Make fsl_esdhc driver happy */
+enum mxc_clock {
+	MXC_ESDHC_CLK,
+};
+
+DECLARE_GLOBAL_DATA_PTR;
+
+uint mxc_get_clock(int clk)
+{
+	return gd->arch.sdhc_clk;
+}
+#endif /* __ASM_POWERPC_CLOCK_H */