riscv: Simplify assignment for UTS_MACHINE

The BITS variable conveniently allows to simplify the assignment for
UTS_MACHINE.

Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@baylibre.com>
Link: https://patch.msgid.link/20260313164012.1153936-2-u.kleine-koenig@baylibre.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>

arch/riscv/Makefile

@@ -28,7 +28,6 @@ endif
 export BITS
 ifeq ($(CONFIG_ARCH_RV64I),y)
 	BITS := 64
-	UTS_MACHINE := riscv64
 
 	KBUILD_CFLAGS += -mabi=lp64
 	KBUILD_AFLAGS += -mabi=lp64
@@ -39,13 +38,14 @@ ifeq ($(CONFIG_ARCH_RV64I),y)
 			    -Cno-redzone
 else
 	BITS := 32
-	UTS_MACHINE := riscv32
 
 	KBUILD_CFLAGS += -mabi=ilp32
 	KBUILD_AFLAGS += -mabi=ilp32
 	KBUILD_LDFLAGS += -melf32lriscv
 endif
 
+UTS_MACHINE := riscv$(BITS)
+
 # LLVM has an issue with target-features and LTO: https://github.com/llvm/llvm-project/issues/59350
 # Ensure it is aware of linker relaxation with LTO, otherwise relocations may
 # be incorrect: https://github.com/llvm/llvm-project/issues/65090