ARM: SAMSUNG: Update default rate for xusbxti clock

The rate of xusbxti clock is set in individual machine files.
The default value should be defined at the clock definition
and individual machine files should modify it if required.

Division by zero in kernel.
[<c0011849>] (unwind_backtrace+0x1/0x9c) from [<c022c663>] (Ldiv0+0x9/0x12)
[<c022c663>] (Ldiv0+0x9/0x12) from [<c001a3c3>] (s3c_setrate_clksrc+0x33/0x78)
[<c001a3c3>] (s3c_setrate_clksrc+0x33/0x78) from [<c0019e67>] (clk_set_rate+0x2f/0x78)

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>