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/include/plat/arm/common/plat_arm.h b/include/plat/arm/common/plat_arm.h
index 0a80814..b0db8f0 100644
--- a/include/plat/arm/common/plat_arm.h
+++ b/include/plat/arm/common/plat_arm.h
@@ -237,6 +237,10 @@
 		uint32_t cookie_lo,
 		void *handle);
 
+/* Optional functions for SP_MIN */
+void plat_arm_sp_min_early_platform_setup(u_register_t arg0, u_register_t arg1,
+			u_register_t arg2, u_register_t arg3);
+
 /* global variables */
 extern plat_psci_ops_t plat_arm_psci_pm_ops;
 extern const mmap_region_t plat_arm_mmap[];