EFI: Do not consider OsIndications variable if CONFIG_EFI_IGNORE_OSINDICATIONS is enabled

The EFI_IGNORE_OSINDICATIONS config symbol was introduced as a
mechanism to have capsule updates work even on platforms where the
SetVariable runtime service was not supported. The current logic
requires the OsIndications variable to have been set to a 64 bit value
even when the EFI_IGNORE_OSINDICATIONS config is enabled. Return an
error code on not being able to read the variable only when
EFI_IGNORE_OSINDICATIONS is not enabled.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>