MIPS: Octeon: Add octeon_get_io_clock_rate() for cn63xx

Starting with cn63xx Octeon I/O blocks are clocked at a different rate
than the CPU.  Add a new function octeon_get_io_clock_rate() that
yields the I/O clock rate.

Also rearrange octeon_get_clock_rate() to get the value from the saved
sysinfo structure.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Patchwork: http://patchwork.linux-mips.org/patch/1671/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/include/asm/octeon/octeon.h b/arch/mips/include/asm/octeon/octeon.h
index 917a6c4..6b34afd0 100644
--- a/arch/mips/include/asm/octeon/octeon.h
+++ b/arch/mips/include/asm/octeon/octeon.h
@@ -35,6 +35,7 @@
 extern int octeon_is_pci_host(void);
 extern int octeon_usb_is_ref_clk(void);
 extern uint64_t octeon_get_clock_rate(void);
+extern u64 octeon_get_io_clock_rate(void);
 extern const char *octeon_board_type_string(void);
 extern const char *octeon_get_pci_interrupts(void);
 extern int octeon_get_southbridge_interrupt(void);