OvmfPkg/SmbiosPlatformDxe: locate SMBIOS protocol in InstallAllStructures()

OvmfPkg/SmbiosPlatformDxe: locate SMBIOS protocol in InstallAllStructures()

Locate the SMBIOS protocol internally to the InstallAllStructures()
function. This has no performance impact (InstallAllStructures() is only
called once), but moving the code from the entry point function makes the
latter smaller. And that will be useful when we split the entry point
function to two versions.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2122
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20210526201446.12554-39-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>