mmc: sdhci: Force probe of shdc1 based on boolean property

Force probing the sdhc1 bus even if it is not the boot device
by reading the device tree property qcom,force-sdhc1-probe.
Enables using the primary port for other use cases even when
the board is not using eMMC for boot.

Change-Id: I2a2b9d6a51037641720bdfd3107b2fadf385d7b5
Signed-off-by: Gustavo Solaira <gustavos@codeaurora.org>