m68k: mac: Fix VIA timer counter accesses

m68k: mac: Fix VIA timer counter accesses

[ Upstream commit 0ca7ce7db771580433bf24454f7a1542bd326078 ]

This resolves some bugs that affect VIA timer counter accesses.
Avoid lost interrupts caused by reading the counter low byte register.
Make allowance for the fact that the counter will be decremented to
0xFFFF before being reloaded.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>