staging: vchiq_core: introduce defines for retry_poll

Use descriptive defines instead of a number with a comment.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/1621106030-30363-1-git-send-email-stefan.wahren@i2se.com


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