soc: mediatek: mtk-svs: Explicitly include bitfield header

Commit a92438c5 ("soc: mediatek: mtk-svs: Use bitfield access macros
where possible") introduced the use of FIELD_GET and FIELD_PREP macros,
which are defined in the bitfield header. Add an explicit include for it
so we're sure to have the symbols defined independently of the config.

Fixes: a92438c5 ("soc: mediatek: mtk-svs: Use bitfield access macros where possible")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220829204439.3748648-1-nfraprado@collabora.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

drivers/soc/mediatek/mtk-svs.c

@@ -3,6 +3,7 @@
  * Copyright (C) 2022 MediaTek Inc.
  */
 
+#include <linux/bitfield.h>
 #include <linux/bits.h>
 #include <linux/clk.h>
 #include <linux/completion.h>