staging: most: dim2: replace BUG_ON() in try_start_dim_transfer()

staging: most: dim2: replace BUG_ON() in try_start_dim_transfer()

Replace BUG_ON() calls with graceful error handling.

For the null/uninitialized channel checks, return -EINVAL instead of
crashing the kernel. For the zero bus_address check, release the
spinlock and return -EFAULT.

BUG_ON() is deprecated as it crashes the entire kernel on assertion
failure (see Documentation/process/deprecated.rst).

Signed-off-by: Gabriel Rondon <grondon@gmail.com>
Link: https://patch.msgid.link/20260330182255.75241-2-grondon@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>