ARM: OMAP5: Redo THUMB mode switch on secondary CPU

Here's a redo of the patch [1] that effectively does the same
thing but is the right way to do things by using ENDPROC instead.
The firmware correctly switches to THUMB before entry.

The patch applies ontop of the earlier patch [1].

[1] https://lkml.org/lkml/2014/4/22/1044



Suggested-by: Dave Martin <Dave.Martin@arm.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Nishanth Menon <nm@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Joel Fernandes <joelf@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>