There is only one caller of tcmu_get_block_page left. Since it is a
one-liner, we can remove the function.

Link: https://lore.kernel.org/r/20210324195758.2021-5-bostroesser@gmail.comSigned-off-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>