cnss: register callback for the cnss bus specific export symbol

For devices with no SDIO connected, it is useless to compile/load
the cnss SDIO platform driver, same for the cnss PCIe platform driver
compile/load for the device with non PCIe interfaced wlan module.
To resolve the above issue compile the cnss SDIO/PCIe platform driver
with cnss bus specific Kconfig flag and register callback for the bus
specific API for the cnss common export symbol.

Instead of directly calling the bus specific APIs, register callback for
the bus specific API and encapsulate the callbacks in device platform_data.
Direct calling of bus specific APIs for the cnss common export symbol
is forcing to compile & load both SDIO and PCIe platform driver even the
wlan module is not interfaced with that bus.

This also helps to reduce the attack surface of kernel.

CRs-Fixed: 1104069
Change-Id: I2d95d083a968d5bd47d4c24438183d22e2ae0c1b
Signed-off-by: Sarada Prasanna Garnayak <sgarna@codeaurora.org>