riscv: Remove redundant judgment for the default build target

The value of KBUILD_IMAGE is derived from $(boot-image-y),
so there's no need for redundant checks before this.

Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
Reviewed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/r/20251029094429.553842-2-jiangfeng@kylinos.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>

Author: flynnjiang

arch/riscv/Makefile

@@ -134,21 +134,6 @@ endif
 CHECKFLAGS += -D__riscv -D__riscv_xlen=$(BITS)
 
 # Default target when executing plain make
-boot		:= arch/riscv/boot
-ifeq ($(CONFIG_XIP_KERNEL),y)
-KBUILD_IMAGE := $(boot)/xipImage
-else
-ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN_K210),yy)
-KBUILD_IMAGE := $(boot)/loader.bin
-else
-ifeq ($(CONFIG_EFI_ZBOOT),)
-KBUILD_IMAGE	:= $(boot)/Image.gz
-else
-KBUILD_IMAGE := $(boot)/vmlinuz.efi
-endif
-endif
-endif
-
 boot					:= arch/riscv/boot
 boot-image-y				:= Image
 boot-image-$(CONFIG_KERNEL_BZIP2)	:= Image.bz2