USB: ehci-omap: fix Si version related programming

AM3517 is based on ES3.1 thus ES2.x related programming is invalid
for it so updating ES2.x programming.

Also fixed below checkpatch warning:
WARNING: unnecessary whitespace before a quoted newline

Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>