arch/{arm64,riscv}: remove jmp_to_elf_entry() declaration

jmp_to_elf_entry() is not defined anywhere. Remove it.

Change-Id: I68f996a735f2ef3dd60cf69f9b72c3f1481cbb55
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13680
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/arch/arm64/include/arch/stages.h

@@ -21,6 +21,5 @@
 extern void main(void);
 
 void stage_entry(void);
-void jmp_to_elf_entry(void *entry, unsigned long buffer, unsigned long size);
 
 #endif

src/arch/riscv/include/arch/stages.h

@@ -19,6 +19,5 @@
 extern void main(void);
 
 void stage_entry(void) __attribute__((section(".text.stage_entry")));
-void jmp_to_elf_entry(void *entry, unsigned long buffer, unsigned long size);
 
 #endif