API: unify platform_sys_info() implementations

ARM, MIPS, and RISCV can use the same implementation of
platform_sys_info(). PPC provides some extra information.
So keep it separate.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/api/Makefile b/api/Makefile
index bd2d035..ce3de6b 100644
--- a/api/Makefile
+++ b/api/Makefile
@@ -1,8 +1,11 @@
-# SPDX-License-Identifier: GPL-2.0+
+# SPDX-License-Identifier: GPL-2.0-or-later
 #
 # (C) Copyright 2007 Semihalf
 
 obj-y += api.o api_display.o api_net.o api_storage.o
-obj-$(CONFIG_ARM) += api_platform-arm.o
+
+ifeq (CONFIG_PPC,y)
 obj-$(CONFIG_PPC) += api_platform-powerpc.o
-obj-$(CONFIG_MIPS) += api_platform-mips.o
+else
+obj-y += api_platform.o
+endif