sunxi: Fix sun5i mbus speed when booting old kernels

Older linux-sunxi-3.4 kernels override our PLL6 setting with 300 MHz,
halving the mbus frequency, so set it to 300 MHz ourselves and base the
mbus divider on that.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>

arch/arm/include/asm/arch-sunxi/clock_sun4i.h

@@ -144,7 +144,16 @@ struct sunxi_ccm_reg {
 
 #define PLL1_CFG_DEFAULT	0xa1005000
 
+#if defined CONFIG_OLD_SUNXI_KERNEL_COMPAT && defined CONFIG_MACH_SUN5I
+/*
+ * Older linux-sunxi-3.4 kernels override our PLL6 setting with 300 MHz,
+ * halving the mbus frequency, so set it to 300 MHz ourselves and base the
+ * mbus divider on that.
+ */
+#define PLL6_CFG_DEFAULT	0xa1009900
+#else
 #define PLL6_CFG_DEFAULT	0xa1009911
+#endif
 
 /* nand clock */
 #define NAND_CLK_SRC_OSC24		0