rx: Remove RX_CALL_IDLE

rx: Remove RX_CALL_IDLE

After change Ie0497d24f1bf4ad7d30ab59061f96c3298f47d17, RX_CALL_IDLE
is not generated by Rx anymore; "idle dead" timeouts just cause
RX_CALL_TIMEOUT errors. Any code dealing with it is thus now dead code
(this value was deliberately never sent over the wire), so remove the
dead code.

Change-Id: I2b38327f77ffc8168712b83506afa1da3eea1224
Reviewed-on: http://gerrit.openafs.org/10783
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>