omap: dpll: module: fix module check and disable cascading by default

According to logs and user's reports dpll cascading causes issues on smartreflex mpu handling and results in freezes, lockups ior reboots when SR for mpu gets enabled.
Probably this is also responsible for sr_enabled_on_init error on TARGA and EDISON. Disabled dpll for now and check on devices.

Due to some wrong code in prior commits this fix could also prevent the battery drain seen on some Targa dn Edison devices..