RDMA/hfi1: Move user SDMA system memory pinning code to its own file

Move user SDMA system memory page-pinning code from user_sdma.c to
pin_system.c. Put declarations for non-static functions in pinning.h.

System memory pinning is necessary for processing user SDMA requests but
actual steps are invisible to user SDMA request-processing code. Moving
system memory pinning code for user SDMA to its own file makes this
distinction apparent.

These changes have no effect on userspace.

Signed-off-by: Patrick Kelsey <pat.kelsey@cornelisnetworks.com>
Signed-off-by: Brendan Cunningham <bcunningham@cornelisnetworks.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Link: https://lore.kernel.org/r/169271327311.1855761.4736714053318724062.stgit@awfm-02.cornelisnetworks.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Author: BrendanCunningham

drivers/infiniband/hw/hfi1/Makefile

@@ -31,6 +31,7 @@ hfi1-y := \
 	netdev_rx.o \
 	opfn.o \
 	pcie.o \
+	pin_system.o \
 	pio.o \
 	pio_copy.o \
 	platform.o \

drivers/infiniband/hw/hfi1/hfi.h

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 or BSD-3-Clause */
 /*
- * Copyright(c) 2020 Cornelis Networks, Inc.
+ * Copyright(c) 2020-2023 Cornelis Networks, Inc.
  * Copyright(c) 2015-2020 Intel Corporation.
  */
 
@@ -1378,8 +1378,6 @@ struct hfi1_devdata {
 #define PT_INVALID        3
 
 struct tid_rb_node;
-struct mmu_rb_node;
-struct mmu_rb_handler;
 
 /* Private data for file operations */
 struct hfi1_filedata {