IB/ipath: Fix incorrect use of sizeof on msg buffer (function argument)

Inside a function declared as

    void foo(char bar[512])

the value of sizeof bar is the size of a pointer, not 512.  So avoid
constructions like this by passing the size explicitly.

Also reduce the size of the buffer to 128 bytes (512 was overly generous).

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>