cxlflash: Fix read capacity timeout

The timeout value for read capacity is too small. Certain devices
may take longer to respond and thus the command may prematurely
timeout. Additionally the literal used for the timeout is stale.

Update the timeout to 30 seconds (matches the value used in sd.c)
and rework the timeout literal to a more appropriate description.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>