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.

Cc: Michael Pavone <pavone@retrodev.com>
Fixes: 7529b90d ("m68k: mvme147: Handle timer counter overflow")
Fixes: 19999a8b ("m68k: mvme16x: Handle timer counter overflow")
Reported-and-tested-by: Michael Pavone <pavone@retrodev.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Link: https://lore.kernel.org/r/4fdaa113db089b8fb607f7dd818479f8cdcc4547.1617089871.git.fthain@telegraphics.com.auSigned-off-by: Geert Uytterhoeven <geert@linux-m68k.org>