[ARM] 3291/1: PXA27x: Correct get_clk_frequency_khz turbo flag handling

Patch from Richard Purdie

The turbo flag is in bit 0 of the CLKCFG register, not bit 1.
This patch corrects this so get_clk_frequency_khz returns a correct
value.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>