infiniband: remove redundant assignment to pointer 'rdi'

The pointer rdi is being initialized with a value that is never read
and re-assigned immediately after, hence the initialization is redundant
and can be removed.

Cleans up clang warning:
drivers/infiniband/sw/rdmavt/vt.c:94:23: warning: Value stored to 'rdi'
during its initialization is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>