tools: elfutils: fix uio header inclusion

tools: elfutils: fix uio header inclusion

Fixes arm64 build failures by replacing <linux/uio.h> with POSIX <sys/uio.h>
to avoid header redefinition conflicts.

gnulib's fcntl.h ends up including glibc's fcntl.h and fcntl-linux.h
which includes glibc's types/struct_iovec.h,
thats where the redefinition happens.

the lines that use <linux/uio.h> are antiquated and were never necessary.
it can be traced back to the original 2014 change that added the file with aarch64 support
in upstream commit 66637fa21044ac0058b25522f473669e73de328b

it was never necessary to use the linux header over the glibc headers,
as elfutils only needs the iovec struct and that struct was present since glibc 2.0 in the 1990s

Signed-off-by: Paweł Owoc <frut3k7@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/24539
Signed-off-by: Robert Marko <robimarko@gmail.com>