refactor(aarch64): rename do_panic and el3_panic

Current panic call invokes do_panic which calls el3_panic, but now panic
handles only panic from EL3 anid clear separation to use lower_el_panic()
which handles panic from lower ELs.

So now we can remove do_panic and just call el3_panic for all panics.

Change-Id: I739c69271b9fb15c1176050877a9b0c0394dc739
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>

include/common/debug.h

@@ -99,14 +99,14 @@ void backtrace(const char *cookie);
 #define backtrace(x)
 #endif
 
-void __dead2 do_panic(void);
+void __dead2 el3_panic(void);
 void __dead2 report_elx_panic(void);
 
 #define panic()				\
 	do {				\
 		backtrace(__func__);	\
 		console_flush();	\
-		do_panic();		\
+		el3_panic();		\
 	} while (false)
 
 #if CRASH_REPORTING