linux-user: fix compat with glibc >= 2.36 sys/mount.h

linux-user: fix compat with glibc >= 2.36 sys/mount.h

The latest glibc 2.36 has extended sys/mount.h so that it
defines the FSCONFIG_* enum constants. These are historically
defined in linux/mount.h, and thus if you include both headers
the compiler complains:

In file included from /usr/include/linux/fs.h:19,
                 from ../linux-user/syscall.c:98:
/usr/include/linux/mount.h:95:6: error: redeclaration of 'enum fsconfig_command'
   95 | enum fsconfig_command {
      |      ^~~~~~~~~~~~~~~~
In file included from ../linux-user/syscall.c:31:
/usr/include/sys/mount.h:189:6: note: originally defined here
  189 | enum fsconfig_command
      |      ^~~~~~~~~~~~~~~~
/usr/include/linux/mount.h:96:9: error: redeclaration of enumerator 'FSCONFIG_SET_FLAG'
   96 |         FSCONFIG_SET_FLAG       = 0,    /* Set parameter, supplying no value */
      |         ^~~~~~~~~~~~~~~~~
/usr/include/sys/mount.h:191:3: note: previous definition of 'FSCONFIG_SET_FLAG' with type 'enum fsconfig_command'
  191 |   FSCONFIG_SET_FLAG       = 0,    /* Set parameter, supplying no value */
      |   ^~~~~~~~~~~~~~~~~
...snip...

QEMU doesn't include linux/mount.h, but it does use
linux/fs.h and thus gets linux/mount.h indirectly.

glibc acknowledges this problem but does not appear to
be intending to fix it in the forseeable future, simply
documenting it as a known incompatibility with no
workaround:

  https://sourceware.org/glibc/wiki/Release/2.36#Usage_of_.3Clinux.2Fmount.h.3E_and_.3Csys.2Fmount.h.3E
  https://sourceware.org/glibc/wiki/Synchronizing_Headers

To address this requires either removing use of sys/mount.h
or linux/fs.h, despite QEMU needing declarations from
both.

This patch removes linux/fs.h, meaning we have to define
various FS_IOC constants that are now unavailable.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Message-Id: <20220802164134.1851910-1-berrange@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>