Fix posix_memalign introduced tag.

Apparently this didn't make it to all android-16 devices. As far as
we know it did make it for all android-17 devices.

Test: make checkbuild
Bug: https://github.com/android-ndk/ndk/issues/647
Change-Id: I2f07cfb1254e2a203c1c10b91b0be46bf37ea853
diff --git a/libc/libc.arm.map b/libc/libc.arm.map
index 56e4189..ee05b16 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -710,7 +710,7 @@
     posix_fallocate; # introduced=21
     posix_fallocate64; # introduced=21
     posix_madvise; # introduced=23
-    posix_memalign; # introduced-arm=16 introduced-arm64=21 introduced-mips=16 introduced-mips64=21 introduced-x86=16 introduced-x86_64=21
+    posix_memalign; # introduced=17
     posix_openpt; # introduced=21
     ppoll; # introduced=21
     prctl;