lib/Kconfig: Remove RAMSTAGE_CBMEM_TOP_ARG

All targets now have the _cbmem_top_ptr symbol populated via calling
arguments or in the nvidia/tegra210 case worked around by populating
it with cbmem_top_chipset explicitly at the start of ramstage, so the
Kconfig guarding this behavior can be removed.

Change-Id: Ie7467629e58700e4d29f6e735840c22ed687f880
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36422
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Michael Niewöhner
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/lib/imd_cbmem.c b/src/lib/imd_cbmem.c
index cbd4b8f..38620d2 100644
--- a/src/lib/imd_cbmem.c
+++ b/src/lib/imd_cbmem.c
@@ -51,16 +51,14 @@
 
 void *cbmem_top(void)
 {
-	if (ENV_ROMSTAGE
-	    || ((ENV_POSTCAR || ENV_RAMSTAGE)
-		&& !CONFIG(RAMSTAGE_CBMEM_TOP_ARG))) {
+	if (ENV_ROMSTAGE) {
 		MAYBE_STATIC_BSS void *top = NULL;
 		if (top)
 			return top;
 		top = cbmem_top_chipset();
 		return top;
 	}
-	if ((ENV_POSTCAR || ENV_RAMSTAGE) && CONFIG(RAMSTAGE_CBMEM_TOP_ARG))
+	if (ENV_POSTCAR || ENV_RAMSTAGE)
 		return (void *)_cbmem_top_ptr;
 
 	dead_code();