Documentation/llvm: Fix clang target examples

clang --target=<triple> is how we can specify a particular toolchain
triple to be use, fix the two occurences in the documentation.

Fixes: fcf1b6a35c16 ("Documentation/llvm: add documentation on building w/ Clang/LLVM")
Signed-off-by: Florian Fainelli <[e-mail]>
Reviewed-by: Nick Desaulniers <[e-mail]>
Reviewed-by: Nathan Chancellor <[e-mail]>
Signed-off-by: Masahiro Yamada <[e-mail]>

Documentation/kbuild/llvm.rst

···
 	ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang
 
 ``CROSS_COMPILE`` is not used to prefix the Clang compiler binary, instead
-``CROSS_COMPILE`` is used to set a command line flag: ``--target <triple>``. For
+``CROSS_COMPILE`` is used to set a command line flag: ``--target=<triple>``. For
 example: ::
 
-	clang --target aarch64-linux-gnu foo.c
+	clang --target=aarch64-linux-gnu foo.c
 
 LLVM Utilities
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