clk: pxa: fix building on older compilers

gcc-4.4 got confused by the inline assembler statement:

drivers/clk/pxa/clk-pxa.c: In function 'pxa2xx_core_turbo_switch':
drivers/clk/pxa/clk-pxa.c:152: error: expected string literal before ')' token

This removes the extraneous ':' to let all compilers parse the
driver correctly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>