fsl/mpc85xx: define common serdes_clock_to_string function

This allows to share some common code for the boards that use a corenet
base SoC.

Two different versions of the function are available in
fsl_corenet_serdes.c and fsl_corenet2_serdes.c files.

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
[York Sun: fix t1040qds.c]
Acked-by: York Sun <yorksun@freescale.com>
diff --git a/arch/powerpc/cpu/mpc85xx/fsl_corenet2_serdes.c b/arch/powerpc/cpu/mpc85xx/fsl_corenet2_serdes.c
index 39d9409..25db899 100644
--- a/arch/powerpc/cpu/mpc85xx/fsl_corenet2_serdes.c
+++ b/arch/powerpc/cpu/mpc85xx/fsl_corenet2_serdes.c
@@ -201,3 +201,24 @@
 #endif
 
 }
+
+const char *serdes_clock_to_string(u32 clock)
+{
+	switch (clock) {
+	case SRDS_PLLCR0_RFCK_SEL_100:
+		return "100";
+	case SRDS_PLLCR0_RFCK_SEL_125:
+		return "125";
+	case SRDS_PLLCR0_RFCK_SEL_156_25:
+		return "156.25";
+	case SRDS_PLLCR0_RFCK_SEL_161_13:
+		return "161.1328123";
+	default:
+#if defined(CONFIG_T4240QDS)
+		return "???";
+#else
+		return "122.88";
+#endif
+	}
+}
+
diff --git a/arch/powerpc/cpu/mpc85xx/fsl_corenet_serdes.c b/arch/powerpc/cpu/mpc85xx/fsl_corenet_serdes.c
index 680b522..ba22f90 100644
--- a/arch/powerpc/cpu/mpc85xx/fsl_corenet_serdes.c
+++ b/arch/powerpc/cpu/mpc85xx/fsl_corenet_serdes.c
@@ -858,3 +858,20 @@
 	}
 #endif
 }
+
+const char *serdes_clock_to_string(u32 clock)
+{
+	switch (clock) {
+	case SRDS_PLLCR0_RFCK_SEL_100:
+		return "100";
+	case SRDS_PLLCR0_RFCK_SEL_125:
+		return "125";
+	case SRDS_PLLCR0_RFCK_SEL_156_25:
+		return "156.25";
+	case SRDS_PLLCR0_RFCK_SEL_161_13:
+		return "161.1328123";
+	default:
+		return "150";
+	}
+}
+
diff --git a/arch/powerpc/include/asm/fsl_serdes.h b/arch/powerpc/include/asm/fsl_serdes.h
index 1106d28..cce892c 100644
--- a/arch/powerpc/include/asm/fsl_serdes.h
+++ b/arch/powerpc/include/asm/fsl_serdes.h
@@ -86,6 +86,7 @@
 
 int is_serdes_configured(enum srds_prtcl device);
 void fsl_serdes_init(void);
+const char *serdes_clock_to_string(u32 clock);
 
 #ifdef CONFIG_FSL_CORENET
 #ifdef CONFIG_SYS_FSL_QORIQ_CHASSIS2