LoongArch: Add some annotations in archhelp

- Add annotations to the kernel image.
- Modify the annotations of make insatll.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: tangyouling

arch/loongarch/Makefile

@@ -184,6 +184,11 @@ install:
 	$(call cmd,install)
 
 define archhelp
-	echo '  install              - install kernel into $(INSTALL_PATH)'
+	echo '  vmlinux.elf    - Uncompressed ELF kernel image (arch/loongarch/boot/vmlinux.elf)'
+	echo '  vmlinux.efi    - Uncompressed EFI kernel image (arch/loongarch/boot/vmlinux.efi)'
+	echo '  vmlinuz.efi    - GZIP/ZSTD-compressed EFI kernel image (arch/loongarch/boot/vmlinuz.efi)'
+	echo '                   Default when CONFIG_EFI_ZBOOT=y'
+	echo '  install        - Install kernel using (your) ~/bin/$(INSTALLKERNEL) or'
+	echo '                   (distribution) /sbin/$(INSTALLKERNEL) or install.sh to $$(INSTALL_PATH)'
 	echo
 endef