sunxi: prcm: Add a few registers

H6 and H616 SPL code has a few writes to unknown PRCM registers. Now
that we know what they are, let's replace magic offsets with proper
register names.

Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/arch/arm/mach-sunxi/clock_sun50i_h6.c b/arch/arm/mach-sunxi/clock_sun50i_h6.c
index a947463..e5846e6 100644
--- a/arch/arm/mach-sunxi/clock_sun50i_h6.c
+++ b/arch/arm/mach-sunxi/clock_sun50i_h6.c
@@ -9,10 +9,12 @@
 {
 	struct sunxi_ccm_reg *const ccm =
 		(struct sunxi_ccm_reg *)SUNXI_CCM_BASE;
+	struct sunxi_prcm_reg *const prcm =
+		(struct sunxi_prcm_reg *)SUNXI_PRCM_BASE;
 
 	/* this seems to enable PLLs on H616 */
 	if (IS_ENABLED(CONFIG_MACH_SUN50I_H616))
-		setbits_le32(SUNXI_PRCM_BASE + 0x250, 0x10);
+		setbits_le32(&prcm->sys_pwroff_gating, 0x10);
 
 	clock_set_pll1(408000000);