torture: Add init-program support for loongarch

This commit adds the __loongarch__, __loongarch_lp64, and
__loongarch_double_float targets to rcutorture's mkinitrd.sh
script in order to allow nolibc init programs for loongarch.

[ paulmck: Apply feedback from Feiyang Chen. ]

Cc: Feiyang Chen <chenfeiyang@loongson.cn>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/mkinitrd.sh

@@ -63,7 +63,7 @@ ___EOF___
 # build using nolibc on supported archs (smaller executable) and fall
 # back to regular glibc on other ones.
 if echo -e "#if __x86_64__||__i386__||__i486__||__i586__||__i686__" \
-           "||__ARM_EABI__||__aarch64__||__s390x__\nyes\n#endif" \
+	   "||__ARM_EABI__||__aarch64__||__s390x__||__loongarch__\nyes\n#endif" \
    | ${CROSS_COMPILE}gcc -E -nostdlib -xc - \
    | grep -q '^yes'; then
 	# architecture supported by nolibc