IB/qib: Remove unused variable (char *qib_sdma_event_names[])

Note: This is compile only tested as I have no access to the hw.

This variable was not used anywhere in the code. Removing it saves 88
bytes.

add/remove: 0/1 grow/shrink: 0/0 up/down: 0/-88 (-88)
Function                                     old     new   delta
qib_sdma_event_names                          88       -     -88
Total: Before=2874565, After=2874477, chg -0.00%

Signed-off-by: Hernán Gonzalez <hernan@vanguardiasur.com.ar>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>