ath10k: fix null dereference on pointer crash_data

Currently when pointer crash_data is null the present null check
will also check that crash_data->ramdump_buf is null and will cause
a null pointer dereference on crash_data. Fix this by using the ||
operator instead of &&.

Fixes: 3f14b73c ("ath10k: Enable MSA region dump support for WCN3990")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>