msm: ipa2: notify sps driver to cache the write pointer for IPA BAM pipes

Due to HW limitation when returning from power-collapse SW shall read the
BAM write pointer value from SW instead of from the HW. This change
sets the SPS_BAM_CACHED_WP flag when IPA BAM registers to SPS driver.

Change-Id: Id287e40431bc483156ca9652f7f4dc565c790d30
Signed-off-by: Nadine Toledano <nadinet@codeaurora.org>