staging: vchiq_shim: avoid code duplication

Rearrange the polling loops in order to avoid code duplication. Btw we fix
the style of the comments.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>