i2c: exynos5: correct top kerneldoc

The top comment is not a kerneldoc, as W=1 build reports:

  drivers/i2c/busses/i2c-exynos5.c:39: warning:
    expecting prototype for i2c(). Prototype was for HSI2C_CTL() instead

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>