Fix "make dist" on recently added architectures

Fix "make dist" on recently added architectures

* Makefile.am (EXTRA_DIST): Add linux/aarch64/errnoent1.h,
linux/aarch64/ioctlent.h.in, linux/aarch64/ioctlent1.h,
linux/aarch64/signalent1.h, linux/aarch64/syscallent.h,
linux/aarch64/syscallent1.h, linux/metag/ioctlent.h.in,
linux/metag/syscallent.h, linux/or1k/ioctlent.h.in,
linux/or1k/syscallent.h, linux/tile/errnoent1.h, linux/tile/ioctlent1.h,
linux/tile/signalent1.h, linux/tile/syscallent1.h, linux/ubi-user.h,
linux/xtensa/ioctlent.h.in, and linux/xtensa/syscallent.h.