device/mmio: Make buffer_to_fifo32() take a const buffer

The input buffer to the buffer_to_fifo family of functions is only read,
so it can be a const pointer. (Also, remove the MIPS check in libpayload
for these functions... the MIPS architecture has been removed a while
ago.)

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I021069680cf691590fdacc3d51f747f12ae3df31
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57731
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

payloads/libpayload/libc/lib.c

@@ -126,7 +126,6 @@ char *getenv(const char *name)
 	return NULL;
 }
 
-#if !CONFIG(LP_ARCH_MIPS)
 /*
  * Reads a transfer buffer from 32-bit FIFO registers. fifo_stride is the
  * distance in bytes between registers (e.g. pass 4 for a normal array of 32-bit
@@ -156,10 +155,10 @@ void buffer_from_fifo32(void *buffer, size_t size, void *fifo,
  * bytes of the 'prefix' u32 parameter and any high-order bytes exceeding prefsz
  * must be 0. Note that 'size' counts total bytes written, including 'prefsz'.
  */
-void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
+void buffer_to_fifo32_prefix(const void *buffer, u32 prefix, int prefsz, size_t size,
 			     void *fifo, int fifo_stride, int fifo_width)
 {
-	u8 *p = buffer;
+	const u8 *p = buffer;
 	int i, j = prefsz;
 
 	assert(fifo_width > 0 && fifo_width <= sizeof(u32) &&
@@ -175,4 +174,3 @@ void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
 	}
 
 }
-#endif