Despite assigning efi_sys_table->{con_in,con_out} to priv->{in,out},
some functions still use the global efi_sys_table->{con_in,con_out}.
Let's restrict globals access to the probe function and have the priv
struct completely describe input and output used in the callbacks.
No functional change.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>