staging: lustre: fixed shadowed variable in socklnd_cb.c

Removed redundant declaration of variable 'tx' in local scope
Fixed: sparse warning:
socklnd_cb.c:2476:41: warning: symbol 'tx' shadows an earlier one
socklnd_cb.c:2435:25: originally declared here

Signed-off-by: Andrew Kanner <andrew.kanner@gmail.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>