efi/riscv: libstub: Fix comment about absolute relocation

We don't want absolute symbols references in the stub, so fix the double
negation in the comment.

Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: XiaoWang1772

drivers/firmware/efi/libstub/Makefile

@@ -146,7 +146,7 @@ STUBCOPY_RELOC-$(CONFIG_ARM64)	:= R_AARCH64_ABS
 
 # For RISC-V, we don't need anything special other than arm64. Keep all the
 # symbols in .init section and make sure that no absolute symbols references
-# doesn't exist.
+# exist.
 STUBCOPY_FLAGS-$(CONFIG_RISCV)	+= --prefix-alloc-sections=.init \
 				   --prefix-symbols=__efistub_
 STUBCOPY_RELOC-$(CONFIG_RISCV)	:= R_RISCV_HI20