smbios: Fix BIOS Characteristics Extension Byte 2

We currently define the EFI support of an SMBIOS table as the third bit of
"BIOS Characteristics Extension Byte 1". The latest DMTF spec defines it
on "BIOS Characteristics Extension Byte 2".

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Remove superfluous assignment.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>