bionic: fix __set_errno for arm64 syscalls that return a 64-bit value

bionic: fix __set_errno for arm64 syscalls that return a 64-bit value

bionic/libc/arch-arm64/syscalls/read.S ends with:
    b.hi __set_errno
    ret
END(read)

If __set_errno returns int, it will set w0 to 0xFFFFFFFF, which means
x0 is 0x00000000FFFFFFFF.  When interpreted as a ssize_t that is
INT_MAX, not -1.

Change __set_errno to return long, which will cause x0 to be set instead
of w0.

Change-Id: I9f9ea0f2995928d2ea240eb2ff7758ecdf0ff412