smbios: move smbios code into a common folder

smbios: move smbios code into a common folder

To share smbios among different architectures, this patch moves SMBIOS
code (smbios.c and smbios.h) from x86 specific folders into new
hw/smbios directories. As a result, CONFIG_SMBIOS=y is defined in
x86 default config files.

Acked-by: Gabriel Somlo <[email protected]>
Tested-by: Gabriel Somlo <[email protected]>
Reviewed-by: Laszlo Ersek <[email protected]>
Tested-by: Leif Lindholm <[email protected]>
Signed-off-by: Wei Huang <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>