STM32H7 support for EMMC cards

[MattKow-Firefly]

I was testing an EMMC adapter card (has an EMMC chip, plugs in to a micro-SD slot) with PX4 1.15 and it was not initializing the EMMC card. I traced the issue to the NuttX function
static int mmcsd_read_csd(FAR struct mmcsd_state_s *priv)
For STM32H7 the alignment for DMA should be 32 byte, not 16 byte. I made changes locally and built and debugged it, and it works now. I will make a Pull Request with the fix.

[MattKow-Firefly]

It's not letting me make a new branch to commit my changes. In drivers/mmcsd/mmcsd_sdio.c the function:
static int mmcsd_read_csd(FAR struct mmcsd_state_s *priv)
The first line:
uint8_t buffer[512] aligned_data(16);
should be aligned to 32, not 16, for STM32H7. Also in the call a few lines after that:
ret = SDIO_DMAPREFLIGHT(priv->dev, buffer, priv->blocksize);
During my debugging, priv->blocksize was not known yet, so it was 0. This should be changed to:
ret = SDIO_DMAPREFLIGHT(priv->dev, buffer, sizeof(buffer));
That's all.

[farhangnaderi]

you can make a branch always on your local and pr to upstream.
Will check the PR.