ArmPlatformPkg/Bds: Fixed potential overflow in EditHIInputStr()

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Signed-off: Olivier Martin <olivier.martin@arm.com>




git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14393 6f19259b-4bc3-4df7-8a09-765794883524