FROMLIST: ARM: amba: Don't read past the end of sysfs "driver_override" buffer

When printing the driver_override parameter when it is 4095 and 4094
bytes long, the printing code would access invalid memory because we
need count + 1 bytes for printing.

Cfr. commits 4efe874a ("PCI: Don't read past the end of sysfs
"driver_override" buffer") and bf563b01 ("driver core: platform:
Don't read past the end of "driver_override" buffer").

Fixes: 3cf38571 ("ARM: 8256/1: driver coamba: add device binding path 'driver_override'")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
(cherry picked from: https://patchwork.kernel.org/patch/10175611/

)
Signed-off-by: Todd Kjos <tkjos@google.com>

Change-Id: I7a9fffc8e3cc775fcf693edae7b42d57c0a375c5