Add global variable sdhc_per_clk for arm/powerpc

The QorIQ eSDHC controller supports two reference clocks. They are
platform clock and periperhal clock. The global variable sdhc_clk
has already been used for platform clock.
This patch is to add another global variable sdhc_per_clk for
periperhal clock, which provides higher frequency and is required
to be used for SD UHS and eMMC HS200/HS400 speed modes.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
diff --git a/arch/arm/include/asm/global_data.h b/arch/arm/include/asm/global_data.h
index 1774014..f23b6bf 100644
--- a/arch/arm/include/asm/global_data.h
+++ b/arch/arm/include/asm/global_data.h
@@ -13,6 +13,10 @@
 	u32 sdhc_clk;
 #endif
 
+#if defined(CONFIG_FSL_ESDHC)
+	u32 sdhc_per_clk;
+#endif
+
 #if defined(CONFIG_U_QE)
 	u32 qe_clk;
 	u32 brg_clk;