quark_se: Correct UART_IRQ_FLAGS to IOAPIC_LEVEL

This patch basically reverts patch "QMSI/uart: Use IOAPIC_EDGE instead
of IOAPIC_LEVEL". The issue with lost UART interrupts is fixed with
following patch: "_loapic_isr_vector_get: fix implementation" which is
a proper way.

Change-Id: I07aa168335827b09db7fcb2486b01585648ff5d6
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>