efi/efi_test: read RuntimeServicesSupported

Since the UEFI 2.8A specification the UEFI enabled firmware provides a
configuration table EFI_RT_PROPERTIES_TABLE which indicates which runtime
services are enabled. The EFI stub reads this table and saves the value of
the field RuntimeServicesSupported internally.

The Firmware Test Suite requires the value to determine if UEFI runtime
services are correctly implemented.

With this patch an IOCTL call is provided to read the value of the field
RuntimeServicesSupported, e.g.

    #define EFI_RUNTIME_GET_SUPPORTED_MASK \
            _IOR('p', 0x0C, unsigned int)
    unsigned int mask;
    fd = open("/dev/efi_test", O_RDWR);
    ret = ioctl(fd, EFI_RUNTIME_GET_SUPPORTED_MASK, &mask);

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/20201127192051.1430-1-xypron.glpk@gmx.de


Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Ivan Hu <ivan.hu@canonical.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>