msm: emac: Use interrupt clear-on-read feature

Update the interrupt routine to make use of interrupt
clear-on-read feature. Interrupt status bits gets cleared
when the interrupt status register is read and there
is no need to write to status register to clear the bits.

Change-Id: I18483853a81070ff6d368f1153d19340017442f6
Signed-off-by: Niranjana Vishwanathapura <nvishwan@codeaurora.org>