Revert "ARM: OMAP4: remove dead kconfig option OMAP4_ERRATA_I688"

This reverts commit 606da4826b.

We actually need this code for proper behaviour of OMAP4, and it needs
fixing a different way other than just removing the code.  Disabling
code which is necessary in the hopes of persuing multiplatform kernels
is a stupid approach.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Richard Woodruff <r-woodruff2@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-omap2/sleep44xx.S

@@ -333,9 +333,11 @@ ENDPROC(omap4_cpu_resume)
 
 #endif	/* defined(CONFIG_SMP) && defined(CONFIG_PM) */
 
+#ifndef CONFIG_OMAP4_ERRATA_I688
 ENTRY(omap_bus_sync)
 	ret	lr
 ENDPROC(omap_bus_sync)
+#endif
 
 ENTRY(omap_do_wfi)
 	stmfd	sp!, {lr}