msm: ep-pcie: Enable global IRQ after enumeration

The global irqs are being enabled before EP driver has completed
successful link enumeration. This causes a race condition where
the BME IRQ is processed before link up causing the link up to
exit before updating the link status. Any further processing results
in LINK_DISABLED error. Avoid this scenario by enabling the global
interrupts after enumeration has finished.

Change-Id: I983a35f461da5d8966cadc9918b5529d16182b47
Signed-off-by: Gauri Joshi <gaurjosh@codeaurora.org>