dt-bindings: display-timing.txt convert non-ascii characters to ascii

Convert non-ascii up and down arrows to '^' and 'v'
Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/display/panel/display-timing.txt

@@ -57,11 +57,11 @@ can be specified.
 The parameters are defined as:
 
   +----------+-------------------------------------+----------+-------+
-  |          |        ↑                            |          |       |
+  |          |        ^                            |          |       |
   |          |        |vback_porch                 |          |       |
-  |          |        ↓                            |          |       |
+  |          |        v                            |          |       |
   +----------#######################################----------+-------+
-  |          #        ↑                            #          |       |
+  |          #        ^                            #          |       |
   |          #        |                            #          |       |
   |  hback   #        |                            #  hfront  | hsync |
   |   porch  #        |       hactive              #  porch   |  len  |
@@ -69,15 +69,15 @@ The parameters are defined as:
   |          #        |                            #          |       |
   |          #        |vactive                     #          |       |
   |          #        |                            #          |       |
-  |          #        ↓                            #          |       |
+  |          #        v                            #          |       |
   +----------#######################################----------+-------+
-  |          |        ↑                            |          |       |
+  |          |        ^                            |          |       |
   |          |        |vfront_porch                |          |       |
-  |          |        ↓                            |          |       |
+  |          |        v                            |          |       |
   +----------+-------------------------------------+----------+-------+
-  |          |        ↑                            |          |       |
+  |          |        ^                            |          |       |
   |          |        |vsync_len                   |          |       |
-  |          |        ↓                            |          |       |
+  |          |        v                            |          |       |
   +----------+-------------------------------------+----------+-------+
 
 Example: