platform/x86: intel_bxtwc_tmu: Remove first level IRQ unmask

Currently in WCOVE PMIC MFD driver, all second level IRQ chips
are chained to the respective first level IRQs. So there is no
need for explicitly unmasking the first level IRQ in this
driver. This patches removes this level 1 IRQ unmask support.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Darren Hart (VMware) <dvhart@infradead.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>