xtensa: move generic-y of exported headers to uapi/asm/Kbuild

Since commit fcc8487d47 ("uapi: export all headers under uapi
directories"), all (and only) headers under uapi directories are
exported, but asm-generic wrappers are still exceptions.

To complete de-coupling the uapi from kernel headers, move generic-y
of exported headers to uapi/asm/Kbuild.

With this change, "make headers_install" will just need to parse
uapi/asm/Kbuild to build up exported headers.

Also, move "generic-y += kprobes.h" up in order to keep the entries
sorted.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/xtensa/include/uapi/asm/Kbuild

@@ -1,3 +1,12 @@
 # UAPI Header export list
 include include/uapi/asm-generic/Kbuild.asm
+
+generic-y += bitsperlong.h
+generic-y += errno.h
+generic-y += fcntl.h
+generic-y += ioctl.h
+generic-y += kvm_para.h
+generic-y += resource.h
 generic-y += siginfo.h
+generic-y += statfs.h
+generic-y += termios.h