ArmPkg/BdsLib: Added support for TFTP servers without 'tsize' extension

Some TFTP servers do not have 'tsize' extension.
This change allows to download files from TFTP servers that do not have
this extension by trying to download the file into a pre-allocated buffer.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>



git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15539 6f19259b-4bc3-4df7-8a09-765794883524