ruby: fix typo in gmp PACKAGECONFIG option

(From OE-Core rev: 9fb931b69ece7f8a644f9e25600bcbbc9266a761)

(From OE-Core rev: a9b55cbec9f5ff11f92f50c529049e83ac898043)

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/ruby/ruby_2.4.2.bb

@@ -20,7 +20,7 @@ PACKAGECONFIG ??= ""
 PACKAGECONFIG += "${@bb.utils.filter('DISTRO_FEATURES', 'ipv6', d)}"
 
 PACKAGECONFIG[valgrind] = "--with-valgrind=yes, --with-valgrind=no, valgrind"
-PACKAGECONFIG[gpm] = "--with-gmp=yes, --with-gmp=no, gmp"
+PACKAGECONFIG[gmp] = "--with-gmp=yes, --with-gmp=no, gmp"
 PACKAGECONFIG[ipv6] = ",--enable-wide-getaddrinfo,"
 
 EXTRA_AUTORECONF += "--exclude=aclocal"