mfd: wcd9xxx: fix no audio issue due to irq failure

on wcd9306, we have dtsi entry to register interrupts
from 0 to 28. But Tapan codec has num_irq initialised
to 31 causing irq_init to fail.
Correct the macro for TAPAN_NUM_IRQS to resolve the
issue.

Change-Id: Ieadc3fee5c7524e31d1697b23e30665a00564516
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>