staging: vchiq_core: introduce SLOT_QUEUE_INDEX_FROM_POS_MASKED

Define a macro which already masked the result of SLOT_QUEUE_INDEX_FROM_POS.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/1618164700-21150-9-git-send-email-stefan.wahren@i2se.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>