IB/rxe: Remove unused variable (char *rxe_qp_state_name[])

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 24 bytes.

add/remove: 0/1 grow/shrink: 0/0 up/down: 0/-24 (-24)
Function                                     old     new   delta
rxe_qp_state_name                             24       -     -24
Total: Before=3348732, After=3348708, chg -0.00%

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