It is wrong to iounmap resources in the normal path of davinci_pm_init()

The 3 ioremap'ed fields of 'pm_config' can be accessed later on in other
functions, so we should return 'success' instead of unrolling everything.

Fixes: aa9aa1ec ("ARM: davinci: PM: rework init, remove platform device")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
[nsekhar@ti.com: commit message and minor style fixes]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>