icnss: Remove icnss_utils

Remove icnss_utils as this module is no longer needed by
ICNSS platform driver. ICNSS has already switched to
WLAN common utility module in net/wireless/cnss_utils.

CRs-fixed: 2093942
Change-Id: I8031ee608a4f4f7899967f6f81a72c8b65797572
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>