fsl_pq_mdio: Fix compiler/sparse warnings (part 1)

fsl_pq_mdio: Fix compiler/sparse warnings (part 1)

commit 1d2397d742b7a2b39b2f09dd9da3b9d1463f55e9 ("fsl_pq_mdio: Add
Suport for etsec2.0 devices") introduced the following warnings:

  CHECK   fsl_pq_mdio.c
fsl_pq_mdio.c:287:22: warning: incorrect type in initializer (different base types)
fsl_pq_mdio.c:287:22:    expected unknown type 11 const *__mptr
fsl_pq_mdio.c:287:22:    got unsigned long long [unsigned] [assigned] [usertype] addr
fsl_pq_mdio.c:287:19: warning: incorrect type in assignment (different base types)
fsl_pq_mdio.c:287:19:    expected unsigned long long [unsigned] [usertype] ioremap_miimcfg
fsl_pq_mdio.c:287:19:    got struct fsl_pq_mdio *<noident>
  CC      fsl_pq_mdio.o
fsl_pq_mdio.c: In function 'fsl_pq_mdio_probe':
fsl_pq_mdio.c:287: warning: initialization makes pointer from integer without a cast
fsl_pq_mdio.c:287: warning: assignment makes integer from pointer without a cast

These warnings are not easy to fix without ugly __force casts. So,
instead of introducing the casts, rework the code to substitute an
offset from an already mapped area. This makes the code a lot simpler
and less duplicated.

Plus, from now on we don't actually map reserved registers on
non-etsec2.0 devices, so we have more chances to catch programming
errors.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>