dt-bindings: power: sbs-battery: re-document "ti,bq20z75"

This compatible property was documented before the driver was renamed to
"SBS" (see commit e57f1b68c4 ("devicetree-bindings: Propagate
bq20z75->sbs rename to dt bindings")). The driver has continued to
support this property as an alternative to "sbs,sbs-battery", and
because we've noticed there are some lingering TI specifics (in the
manufacturer-specific portion of the SBS spec), we'd like to start using
this property again to differentiate.

In typical DT fashion, the <vendor>,<part-number> specifics should be
used ahead of the generic "sbs,sbs-battery" string, so we can handle
vendor specifics -- so document this. Language borrowed mostly from
Documentation/devicetree/bindings/power/supply/sbs_sbs-charger.txt

Also fixup the example to use this property (it's already implying that
it's "bq20z75@b"); fixup the node name to be generic ("battery", not
"<part-number>"); and fixup some whitespace.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Rhyland Klein <rklein@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

Documentation/devicetree/bindings/power/supply/sbs_sbs-battery.txt

@@ -2,7 +2,11 @@ SBS sbs-battery
 ~~~~~~~~~~
 
 Required properties :
- - compatible : "sbs,sbs-battery"
+ - compatible: "<vendor>,<part-number>", "sbs,sbs-battery" as fallback. The
+     part number compatible string might be used in order to take care of
+     vendor specific registers.
+     Known <vendor>,<part-number>:
+       ti,bq20z75
 
 Optional properties :
  - sbs,i2c-retry-count : The number of times to retry i2c transactions on i2c
@@ -14,9 +18,9 @@ Optional properties :
 
 Example:
 
-	bq20z75@b {
-		compatible = "sbs,sbs-battery";
-		reg = < 0xb >;
+	battery@b {
+		compatible = "ti,bq20z75", "sbs,sbs-battery";
+		reg = <0xb>;
 		sbs,i2c-retry-count = <2>;
 		sbs,poll-retry-count = <10>;
 		sbs,battery-detect-gpios = <&gpio-controller 122 1>;