staging: tidspbridge: detect wdt3 feature at runtime

In order to detect WDT feature on the dsp code, we need to
find the symbol used to enable it inside the baseimage.

This should fix the warning comming from L3 driver:

    WARNING: at arch/arm/mach-omap2/omap_l3_smx.c:161 omap3_l3_app_irq...
    In-band Error seen by IVA_SS  at address 0
    ...

That occurs because the dsp tries to access wdt3 registers when the clock
for those registers is not enabled.

Reported-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Omar Ramirez Luna <omar.ramirez@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>