Remove fiber/isr_tick_get[_32]() APIs

Removes the following context based APIs:
	isr_tick_get_()
	isr_tick_get_32()
	fiber_tick_get()
	fiber_tick_get_32()
The routines sys_tick_get() and sys_tick_get_32() are to be used instead.

Change-Id: I3fa1338f174b10e783bfb00941edadfff16eeaba
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>