ASoC: apr: Add separate initial boot flag for ADSP and Modem

apr ignores initial PDR_DOWN event from ADSP/Modem during
boot up. ADSP_DOWN event is wrongly sent to audio drivers
during boot up if it gets MODEM_UP event before ADSP_DOWN.

Added separate flags for both ADSP and Modem events to avoid
this issue.

CRs-Fixed: 2232315
Change-Id: I2c6084ac03e3867009f36be36631f881124f59ba
Signed-off-by: Soumya Managoli <smanag@codeaurora.org>