riscv: delete temporary files

Temporary files used in the VDSO build process linger on even after make
mrproper: vdso-dummy.o.tmp, vdso.so.dbg.tmp.

Delete them once they're no longer needed.
Signed-off-by: Ilie Halip <ilie.halip@gmail.com>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/kernel/vdso/Makefile

@@ -58,7 +58,8 @@ quiet_cmd_vdsold = VDSOLD  $@
       cmd_vdsold = $(CC) $(KBUILD_CFLAGS) $(call cc-option, -no-pie) -nostdlib -nostartfiles $(SYSCFLAGS_$(@F)) \
                            -Wl,-T,$(filter-out FORCE,$^) -o $@.tmp && \
                    $(CROSS_COMPILE)objcopy \
-                           $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@
+                           $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
+                   rm $@.tmp
 
 # install commands for the unstripped file
 quiet_cmd_vdso_install = INSTALL $@