devicetree: bindings: Add vendor prefix for Micron Technology, Inc.

This patch is used to add vendor prefix for Micron Technology, Inc. in
the vendor-prefixes.txt file.

Micron Technology, Inc. is an American multinational corporation based
in Boise, Idaho, best known for producing many forms of semiconductor
devices. This includes DRAM, SDRAM, flash memory, eMMC and SSDs.

Signed-off-by: Bean Huo <[e-mail]>
[robh: cleanup commit msg formatting and company name]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/vendor-prefixes.txt

···
 mediatek	MediaTek Inc.
 micrel	Micrel Inc.
 microchip	Microchip Technology Inc.
+micron	Micron Technology Inc.
 mitsubishi	Mitsubishi Electric Corporation
 mosaixtech	Mosaix Technologies, Inc.
 moxa	Moxa