fsl_upm: Add MxMR/MDR synchronization

According to Freescale reference manuals (eg section "13.4.4.2
Programming the UPMs" of the P4080 Reference Manual):

"Since the result of any update to the MxMR/MDR register must be in
effect before the dummy read or write to the UPM region, a write to
MxMR/MDR should be followed immediately by a read of MxMR/MDR."

The UPM on a custom P4080-based board did not work without performing
a read of MxMR/MDR after a write.

Signed-off-by: John Schmoller <jschmoller@xes-inc.com>
Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

drivers/mtd/nand/fsl_upm.c

@@ -21,6 +21,7 @@
 static void fsl_upm_start_pattern(struct fsl_upm *upm, u32 pat_offset)
 {
 	clrsetbits_be32(upm->mxmr, MxMR_MAD_MSK, MxMR_OP_RUNP | pat_offset);
+	(void)in_be32(upm->mxmr);
 }
 
 static void fsl_upm_end_pattern(struct fsl_upm *upm)
@@ -35,6 +36,7 @@ static void fsl_upm_run_pattern(struct fsl_upm *upm, int width,
 				void __iomem *io_addr, u32 mar)
 {
 	out_be32(upm->mar, mar);
+	(void)in_be32(upm->mar);
 	switch (width) {
 	case 8:
 		out_8(io_addr, 0x0);