Kernel: Mark SDHC InterruptStatus structured view as const

This view is really nice to check flags, but when clearing them we must
make sure that we only ever try to set 1 bit at a time, which makes
setting bits through the structured view a footgun, as that fetches,
ors in and then sets, potentially resetting other flags.

Kernel/Devices/Storage/SD/Registers.h

@@ -103,7 +103,7 @@ struct HostControlRegisterMap {
             u32 tuning_error : 1;
             u32 response_error : 1;
             u32 vendor_specific_error : 1;
-        };
+        } const;
         u32 raw;
     } interrupt_status;
     u32 interrupt_status_enable;