clk: aspeed: Prevent reset if clock is enabled

According to the Aspeed specification, the reset and enable sequence
should be done when the clock is stopped. The specification doesn't
define behavior if the reset is done while the clock is enabled.

From testing on the AST2500, the LPC Controller has problems if the
clock is reset while enabled.

Therefore, check whether the clock is enabled or not before performing
the reset and enable sequence in the Aspeed clock driver.

Reported-by: Lei Yu <mine260309@gmail.com>
Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
Fixes: 15ed8ce5 ("clk: aspeed: Register gated clocks")
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>