refactor(cm): remove el1 context when SPMD_SPM_AT_SEL2=1

* Currently, EL1 context is included in cpu_context_t by default
  for all the build configurations.
  As part of the cpu context structure, we hold a copy of EL1, EL2
  system registers, per world per PE. This context structure is
  enormous and will continue to grow bigger with the addition of
  new features incorporating  new registers.

* Ideally, EL3 should save and restore the system registers at its next
  lower exception level, which is EL2 in majority of the configurations.

* This patch aims at optimising the memory allocation in cases, when
  the members from the context structure are unused. So el1 system
  register context must be omitted when lower EL is always x-EL2.

* "CTX_INCLUDE_EL2_REGS" is the internal build flag which gets set,
  when SPD=spmd and SPMD_SPM_AT_SEL2=1 or ENABLE_RME=1.
  It indicates, the system registers at EL2 are context switched for
  the respective build configuration. Here, there is no need  to save
  and restore EL1 system registers, while x-EL2 is enabled.

Henceforth, this patch addresses this issue, by taking out the EL1
context at all possible places, while EL2 (CTX_INCLUDE_EL2_REGS) is
enabled, there by saving memory.

Change-Id: Ifddc497d3c810e22a15b1c227a731bcc133c2f4a
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
diff --git a/include/lib/el3_runtime/context_mgmt.h b/include/lib/el3_runtime/context_mgmt.h
index b7b73e6..70dbd46 100644
--- a/include/lib/el3_runtime/context_mgmt.h
+++ b/include/lib/el3_runtime/context_mgmt.h
@@ -47,13 +47,14 @@
 void cm_handle_asymmetric_features(void);
 #endif
 
-#if CTX_INCLUDE_EL2_REGS
+#if (CTX_INCLUDE_EL2_REGS && IMAGE_BL31)
 void cm_el2_sysregs_context_save(uint32_t security_state);
 void cm_el2_sysregs_context_restore(uint32_t security_state);
-#endif
-
+#else
 void cm_el1_sysregs_context_save(uint32_t security_state);
 void cm_el1_sysregs_context_restore(uint32_t security_state);
+#endif /* (CTX_INCLUDE_EL2_REGS && IMAGE_BL31) */
+
 void cm_set_elr_el3(uint32_t security_state, uintptr_t entrypoint);
 void cm_set_elr_spsr_el3(uint32_t security_state,
 			uintptr_t entrypoint, uint32_t spsr);