mmc: core: Make tuning block patterns static

Since previous patches removed the need for the tuning block patterns
to be exported, let's move them close to the mmc_send_tuning() API.

Those are now intended to be used only by the mmc core.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>