ARM: OMAP: hwmod code: remove unused hwmod function prototypes

Several hwmod function prototypes appear to not have an implementation
because the corresponding functions were removed or renamed.
Those prototypes are unneeded anymore - remove them.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
[paul@pwsan.com: tweaked subject]
Signed-off-by: Paul Walmsley <paul@pwsan.com>