Changed to use accessors instead of casting to volatile pointers.

In places where we were defining memory mapped peripheral buffers we
were using directly a cast to "volatile int_type *". For consistency we
should use dereferenced accessor like: &MMIO32(address)

include/libopencm3/stm32/otg_hs.h

@@ -145,8 +145,7 @@
 #define OTG_HS_PCGCCTL			MMIO32(USB_OTG_HS_BASE + OTG_PCGCCTL)
 
 /* Data FIFO */
-#define OTG_HS_FIFO(x)			((volatile uint32_t*)(USB_OTG_HS_BASE \
-							      + OTG_FIFO(x)))
+#define OTG_HS_FIFO(x)			(&MMIO32(USB_OTG_HS_BASE + OTG_FIFO(x)))
 
 /* Global CSRs */
 /* OTG_HS USB control registers (OTG_FS_GOTGCTL) */