Introduce new shared function remote_fileio_to_fio_error

Introduce new shared function remote_fileio_to_fio_error

This commit introduces a new shared function to replace three
identical functions in various places in the codebase.

gdb/ChangeLog:

	* common/common-remote-fileio.h (remote_fileio_to_fio_error):
	New declaration.
	* common/common-remote-fileio.c (remote_fileio_to_fio_error):
	New function, factored out the named functions below.
	* inf-child.c (gdb/fileio.h): Remove include.
	(common-remote-fileio.h): New include.
	(inf_child_errno_to_fileio_error): Remove function.  Update
	all callers to use remote_fileio_to_fio_error.
	* remote-fileio.c (remote_fileio_errno_to_target): Likewise.

gdb/gdbserver/ChangeLog:

	* hostio-errno.c (errno_to_fileio_error): Remove function.
	Update caller to use remote_fileio_to_fio_error.