m68k: mvme147,mvme16x: Don't wipe PCC timer config bits

In the Linux kernel, the following vulnerability has been resolved:

m68k: mvme147,mvme16x: Don't wipe PCC timer config bits

Don't clear the timer 1 configuration bits when clearing the interrupt flag

and counter overflow. As Michael reported, "This results in no timer

interrupts being delivered after the first. Initialization then hangs

in calibrate_delay as the jiffies counter is not updated."

On mvme16x, enable the timer after requesting the irq, consistent with

mvme147.