efi_loader: efi_current_var after SetVirtualAddressMap

Variable efi_current_var is a pointer to a physical memory address that
becomes invalid after SetVirtualAddressMap(). Instead of converting it via
ConvertPointer() simply set it to NULL.

Fixes: b02a707152 ("efi_loader: enable UEFI variables at runtime")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

lib/efi_loader/efi_var_mem.c

@@ -231,6 +231,7 @@ static void EFIAPI __efi_runtime
 efi_var_mem_notify_virtual_address_map(struct efi_event *event, void *context)
 {
 	efi_convert_pointer(0, (void **)&efi_var_buf);
+	efi_current_var = NULL;
 }
 
 efi_status_t efi_var_mem_init(void)