Initial work for the mmc_disk driver

No read and write support for now. But we implement getting SD card
capacity. SDHC is not supported yet (it uses a different layout for the
CSD register which will be rejected by this version of the code)

Change-Id: Ife844a62f3846c0a780259e9a3a08195e2fd965e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1068
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

SDHCI MMC Driver

1. SDHCI PCI Bus: Discovering SDHC device from the PCI bus
and registers a child node(MMC bus) to which slots
are attached. SDHC registers are mapped by MMUIO,
they are binded in a structure(struct* registers).
A pin based interrupt handler is also installed,
which triggers the handler function and interrupts
are being taken care of. Added API's to set-up and
the clock for SD/MMC card, change frequency and
reset the registers.

2. Device Manager: Currently, busses subdir lists are har-
dcoded and in order to load the driver. We hard
coded the bus dir under PCI devices.

3. MMC Disk Driver: In order to register the slots under
/dev/disk/mmc and hence data transfer and other
operations can be done.

4. MMC Bus Manager: Setted up a bus manager to create an object
to do a particular for eg certain data transfer and
get freed until another operation is requested.

Change-Id: I369354da6b79adc6b6dfb08fe160334af1392a34
Reviewed-on: https://review.haiku-os.org/318
Reviewed-by: Alexander von Gluck IV <kallisti5@unixzen.com>