arm: mach-rmobile: Mark the default s_init function as weak

Mark the default s_init function as weak, so that SoC's can
override it if needed, and it will still be discarded if unused.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
diff --git a/arch/arm/mach-rmobile/lowlevel_init_gen3.S b/arch/arm/mach-rmobile/lowlevel_init_gen3.S
index 213ec14..1df2c40 100644
--- a/arch/arm/mach-rmobile/lowlevel_init_gen3.S
+++ b/arch/arm/mach-rmobile/lowlevel_init_gen3.S
@@ -31,6 +31,12 @@
 	b	save_boot_params_ret
 ENDPROC(save_boot_params)
 
+.pushsection .text.s_init, "ax"
+WEAK(s_init)
+	ret
+ENDPROC(s_init)
+.popsection
+
 ENTRY(lowlevel_init)
 	mov	x29, lr			/* Save LR */