x86: doc: move x86-generic documentation from Doc/x86/i386

The boot protocol, USB legacy support, and zero-page documentation is
common to the x86 platform, not i386-specific.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/Documentation/x86/i386/boot.txt b/Documentation/x86/boot.txt
similarity index 100%
rename from Documentation/x86/i386/boot.txt
rename to Documentation/x86/boot.txt

diff --git a/Documentation/x86/i386/usb-legacy-support.txt b/Documentation/x86/usb-legacy-support.txt
similarity index 100%
rename from Documentation/x86/i386/usb-legacy-support.txt
rename to Documentation/x86/usb-legacy-support.txt

diff --git a/Documentation/x86/i386/zero-page.txt b/Documentation/x86/zero-page.txt
similarity index 100%
rename from Documentation/x86/i386/zero-page.txt
rename to Documentation/x86/zero-page.txt