mfd: dt-bindings: atmel-gpbr: Rename doc file to conform to naming convention

Cc: boris.brezillon@free-electrons.com
Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --git a/Documentation/devicetree/bindings/mfd/atmel,gpbr.txt b/Documentation/devicetree/bindings/mfd/atmel-gpbr.txt
similarity index 100%
rename from Documentation/devicetree/bindings/mfd/atmel,gpbr.txt
rename to Documentation/devicetree/bindings/mfd/atmel-gpbr.txt