IB/ehca: Make symbols used only in a single source file static

IB/ehca: Make symbols used only in a single source file static

Allow the compiler to optimize better and generate smaller code:

add/remove: 0/6 grow/shrink: 2/0 up/down: 1528/-1864 (-336)
function                                     old     new   delta
.ehca_set_pagebuf                           1344    2172    +828
.ehca_probe                                 2312    3012    +700
ehca_set_pagebuf_phys                         24       -     -24
ehca_set_pagebuf_fmr                          24       -     -24
ehca_init_device                              24       -     -24
.ehca_set_pagebuf_fmr                        480       -    -480
.ehca_set_pagebuf_phys                       512       -    -512
.ehca_init_device                            800       -    -800

Also this fixes warnings like:

    drivers/infiniband/hw/ehca/ehca_mrmw.c:2015:5: warning: symbol 'ehca_set_pagebuf_fmr' was not declared. Should it be static?

Signed-off-by: Roland Dreier <rolandd@cisco.com>