ntb: intel: constify ioreadX() iomem argument (as in generic implementation)

The ioreadX() helpers have inconsistent interface.  On some architectures
void *__iomem address argument is a pointer to const, on some not.

Implementations of ioreadX() do not modify the memory under the address so
they can be converted to a "const" version for const-safety and
consistency among architectures.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Cc: Allen Hubbe <allenbh@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jon Mason <jdmason@kudzu.us>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/20200709072837.5869-4-krzk@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: krzk

drivers/ntb/hw/intel/ntb_hw_gen1.c

@@ -1205,7 +1205,7 @@ int intel_ntb_peer_spad_write(struct ntb_dev *ntb, int pidx, int sidx,
 			       ndev->peer_reg->spad);
 }
 
-static u64 xeon_db_ioread(void __iomem *mmio)
+static u64 xeon_db_ioread(const void __iomem *mmio)
 {
 	return (u64)ioread16(mmio);
 }

drivers/ntb/hw/intel/ntb_hw_gen3.h

@@ -91,7 +91,7 @@
 #define GEN3_DB_TOTAL_SHIFT		33
 #define GEN3_SPAD_COUNT			16
 
-static inline u64 gen3_db_ioread(void __iomem *mmio)
+static inline u64 gen3_db_ioread(const void __iomem *mmio)
 {
 	return ioread64(mmio);
 }

drivers/ntb/hw/intel/ntb_hw_intel.h

@@ -103,7 +103,7 @@ struct intel_ntb_dev;
 struct intel_ntb_reg {
 	int (*poll_link)(struct intel_ntb_dev *ndev);
 	int (*link_is_up)(struct intel_ntb_dev *ndev);
-	u64 (*db_ioread)(void __iomem *mmio);
+	u64 (*db_ioread)(const void __iomem *mmio);
 	void (*db_iowrite)(u64 db_bits, void __iomem *mmio);
 	unsigned long			ntb_ctl;
 	resource_size_t			db_size;