Build fix - pre-processor typos in rx_lwp.c and rx_pthread.c

Build fix - pre-processor typos in rx_lwp.c and rx_pthread.c

Commit 119c756d96c4a7f9e01e4ff6bb20156f1abf761b introduced a typo
in two places, using #elif instead of the apparently intended #else.

Reviewed-on: http://gerrit.openafs.org/231
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 9a490c96a074f4c3c82a3f01c18bc74cc19ae184)
Change-Id: Ic6282bb1535c0d4ba206736d1c2ae5c088bf2a7e
Reviewed-on: http://gerrit.openafs.org/944
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>