feat(ff-a): partition information via registers

This patch enables basic support for getting partition information via
the ffa_partition_info_get_regs abi. This interface can be used to query
partition information in the absence of rx/tx buffer or when using
memory is inconvenient (such as early boot loaders etc). The patch adds
the required calls, a few helper functions and enables the use of x8-x17
as return values, that is required for this abi to work.

Signed-off-by: Raghu Krishnamurthy <raghu.ncstate@gmail.com>
Change-Id: I70ed78e809a5bf77d77a49e5bc122c1989303ebb
diff --git a/include/runtime_services/ffa_svc.h b/include/runtime_services/ffa_svc.h
index 6236ae3..bf535ea 100644
--- a/include/runtime_services/ffa_svc.h
+++ b/include/runtime_services/ffa_svc.h
@@ -100,6 +100,7 @@
 #define FFA_FNUM_SPM_ID_GET			U(0x85)
 #define FFA_FNUM_MSG_SEND2			U(0x86)
 #define FFA_FNUM_SECONDARY_EP_REGISTER		U(0x87)
+#define FFA_FNUM_PARTITION_INFO_GET_REGS	U(0x8B)
 
 /* Implementation defined function numbers */
 #define FFA_FNUM_CONSOLE_LOG			U(0x8A)
@@ -165,6 +166,8 @@
 	FFA_FID(SMC_64, FFA_FNUM_NOTIFICATION_INFO_GET)
 
 #define FFA_FEATURES_MEM_RETRIEVE_REQ_NS_SUPPORT (UINT32_C(1) << 1)
+#define FFA_PARTITION_INFO_GET_REGS_SMC64 \
+	FFA_FID(SMC_64, FFA_FNUM_PARTITION_INFO_GET_REGS)
 
 /* Implementation defined SMC64 FIDs */
 #define FFA_CONSOLE_LOG_SMC64	FFA_FID(SMC_64, FFA_FNUM_CONSOLE_LOG)