fs: Use ARCH_DMA_MINALIGN as default alignment for fs_read_alloc()

fs: Use ARCH_DMA_MINALIGN as default alignment for fs_read_alloc()

The comment above fs_read_alloc() explains:

    @align: Alignment to use for memory allocation (0 for default)

However, in the actual implementation, there is no alignment when @align is
zero.

This current default is probably fine for most cases. But for some block
devices which transfer data via DMA, ARCH_DMA_MINALIGN is needed.

Change the default alignment to ARCH_DMA_MINALIGN.

Fixes: de7b5a8a1ac0 ("fs: Create functions to load and allocate a file")
Signed-off-by: Nam Cao <namcao@linutronix.de>
Tested-by: Javier Fernandez Pastrana <javier.pastrana@linutronix.de>