board: ns3: add api to save boot parameters passed from BL31

Add API to save boot parameters passed from BL31

Use assembly implementation of save_boot_params instead of c function.
Because generally ATF does not set up SP_EL2 on exiting.
Thus, usage of a C function immediately after exiting with no stack
setup done by ATF explicitly, may cause SP_EL2 to be not sane,
which in turn causes a crash if this boot was not lucky to get
an SP_EL2 in valid range. Replace C implementation with assembly one
which does not use stack this early, and let u-boot to set up its stack
later.

Signed-off-by: Abhishek Shah <abhishek.shah@broadcom.com>
Signed-off-by: Rajesh Ravi <rajesh.ravi@broadcom.com>
Signed-off-by: Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>
Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/cpu/armv8/bcmns3/lowlevel.S b/arch/arm/cpu/armv8/bcmns3/lowlevel.S
index 6709c9a..bf1a17a 100644
--- a/arch/arm/cpu/armv8/bcmns3/lowlevel.S
+++ b/arch/arm/cpu/armv8/bcmns3/lowlevel.S
@@ -87,3 +87,12 @@
 	mov	lr, x29
 	ret
 ENDPROC(__asm_flush_l3_dcache)
+
+ENTRY(save_boot_params)
+/*
+ * void set_boot_params(uint64_t x0, uint64_t x1, uint64_t x2, uint64_t x3)
+ */
+	adr	x4, bl33_info
+	str	x0, [x4]
+	b	save_boot_params_ret
+ENDPROC(save_boot_params)