Remove sp_min functions from plat_common.c

This patch removes default platform implementations of sp_min
platform APIs from plat/common/aarch32/plat_common.c. The APIs
are now implemented in `plat_sp_min_common.c` file within the
same folder.

The ARM platform layer had a weak definition of sp_min_platform_setup2()
which conflicted with the weak definition in the common file. Hence this
patch fixes that by introducing a `plat_arm_` version of the API thus
allowing individual boards within ARM platforms to override it if they
wish to.

Fixes ARM-software/tf-issues#559

Change-Id: I11a74ecae8191878ccc7ea03f12bdd5ae88faba5
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
diff --git a/bl32/sp_min/sp_min.mk b/bl32/sp_min/sp_min.mk
index 145820e..193b1d5 100644
--- a/bl32/sp_min/sp_min.mk
+++ b/bl32/sp_min/sp_min.mk
@@ -15,6 +15,7 @@
 BL32_SOURCES		+=	bl32/sp_min/sp_min_main.c		\
 				bl32/sp_min/aarch32/entrypoint.S	\
 				common/runtime_svc.c			\
+				plat/common/aarch32/plat_sp_min_common.c\
 				services/std_svc/std_svc_setup.c	\
 				${PSCI_LIB_SOURCES}