net: stmmac: dwmac-rk: switch to FIELD_PREP_WM16 macro

The era of hand-rolled HIWORD_UPDATE macros is over, at least for those
drivers that use constant masks.

Like many other Rockchip drivers, dwmac-rk has its own HIWORD_UPDATE
macro. Its semantics allow us to redefine it as a wrapper to the shared
hw_bitfield.h FIELD_PREP_WM16 macros though.

Replace the implementation of this driver's very own HIWORD_UPDATE macro
with an instance of FIELD_PREP_WM16 from hw_bitfield.h. This keeps the
diff easily reviewable, while giving us more compile-time error
checking.

The related GRF_BIT macro is left alone for now; any attempt to rework
the code to not use its own solution here would likely end up harder to
review and less pretty for the time being.

Signed-off-by: Nicolas Frattaroli <[e-mail]>
Acked-by: Jakub Kicinski <[e-mail]>
Acked-by: Heiko Stuebner <[e-mail]>
Signed-off-by: Yury Norov (NVIDIA) <[e-mail]>

drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c

···
  */
 
 #include <linux/stmmac.h>
+#include <linux/hw_bitfield.h>
 #include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/phy.h>
···
 }
 
 #define HIWORD_UPDATE(val, mask, shift) \
-		((val) << (shift) | (mask) << ((shift) + 16))
+		(FIELD_PREP_WM16((mask) << (shift), (val)))
 
 #define GRF_BIT(nr)	(BIT(nr) | BIT(nr+16))
 #define GRF_CLR_BIT(nr)	(BIT(nr+16))