ARM: OMAP2+: Fix broken gpmc support

Commit 6797b4fe (ARM: OMAP2+: Prevent potential crash if GPMC probe fails)
added code to ensure that GPMC chip-selects could not be requested until the
device probe was successful. The chip-selects should have been
unreserved at the end of the probe function, but the code to unreserve
them appears to have ended up in the gpmc_calc_timings() function and
hence, this is causing problems requesting chip-selects. Fix this merge
error by unreserving the chip-selects at the end of the probe, but
before we call the gpmc child probe functions (for device-tree) which
request a chip-select.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Tested-by: Philip Avinash <avinashphilip@ti.com>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>
[tony@atomide.com: updated description to add breaking commit id]
Signed-off-by: Tony Lindgren <tony@atomide.com>