ASoC: wcd-dsp-mgr: rename wdsp_intr_handler to wdsp_signal_handler

The wdsp_intr_handler is not really processing interrupts in interrupt
context, rather assumes that the caller is not in interrupt context and
performs calls that may sleep. Rename the function in order to avoid
confusion. Interrupt handlers can still call this function as long as
they are in threaded interrupt context and are okay to sleep.

Change-Id: Ia2803d6ca021d505ed2e711e676cbd701b11c492
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>