i2c: pasemi: Move common reset code to own function

Split out common reset call to its own function so that we
can later add support for selecting the clock frequency
and an additional enable bit found in newer revisions.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Acked-by: Olof Johansson <olof@lixom.net>
Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>