plat: marvell: do not rely on argument passed via smc

There is no need to rely on x1 argument.

Signed-off-by: Grzegorz Jaszczyk <jaz@semihalf.com>
Change-Id: Ie7766e801e724801b42b66331ba252ede5744a2c
diff --git a/plat/marvell/common/mrvl_sip_svc.c b/plat/marvell/common/mrvl_sip_svc.c
index 36cada1..0291024 100644
--- a/plat/marvell/common/mrvl_sip_svc.c
+++ b/plat/marvell/common/mrvl_sip_svc.c
@@ -116,8 +116,7 @@
 
 	/* Miscellaneous FID's' */
 	case MV_SIP_DRAM_SIZE:
-		/* x1:  ap_base_addr */
-		ret = mvebu_get_dram_size(x1);
+		ret = mvebu_get_dram_size(MVEBU_REGS_BASE);
 		SMC_RET1(handle, ret);
 	case MV_SIP_LLC_ENABLE:
 		for (i = 0; i < ap_get_count(); i++)