Fix lockdep splat introduced in v4.13-rc4.

[  266.297226] ------------[ cut here ]------------
[  266.300078] WARNING: CPU: 2 PID: 176 at /mnt/src/jaja/git/tf300t/include/linux/blkdev.h:657 mmc_blk_remove_req+0xd0/0xe8 [mmc_block]
[  266.302937] Modules linked in: mmc_block(-) sdhci_tegra sdhci_pltfm sdhci pwrseq_simple pwrseq_emmc mmc_core
[  266.305941] CPU: 2 PID: 176 Comm: rmmod Tainted: G        W       4.13.0-rc4mq-00208-gb691e67724b8-dirty #694
[  266.308852] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
[  266.311719] [<b011144c>] (unwind_backtrace) from [<b010ca54>] (show_stack+0x18/0x1c)
[  266.314664] [<b010ca54>] (show_stack) from [<b062e3f4>] (dump_stack+0x84/0x98)
[  266.317644] [<b062e3f4>] (dump_stack) from [<b01214f4>] (__warn+0xf4/0x10c)
[  266.320542] [<b01214f4>] (__warn) from [<b01215d4>] (warn_slowpath_null+0x28/0x30)
[  266.323534] [<b01215d4>] (warn_slowpath_null) from [<af067858>] (mmc_blk_remove_req+0xd0/0xe8 [mmc_block])
[  266.326568] [<af067858>] (mmc_blk_remove_req [mmc_block]) from [<af068f40>] (mmc_blk_remove_parts.constprop.6+0x50/0x64 [mmc_block])
[  266.329678] [<af068f40>] (mmc_blk_remove_parts.constprop.6 [mmc_block]) from [<af0693b8>] (mmc_blk_remove+0x24/0x140 [mmc_block])
[  266.332894] [<af0693b8>] (mmc_blk_remove [mmc_block]) from [<af0052ec>] (mmc_bus_remove+0x20/0x28 [mmc_core])
[  266.336198] [<af0052ec>] (mmc_bus_remove [mmc_core]) from [<b046aa64>] (device_release_driver_internal+0x164/0x200)
[  266.339367] [<b046aa64>] (device_release_driver_internal) from [<b046ab54>] (driver_detach+0x40/0x74)
[  266.342537] [<b046ab54>] (driver_detach) from [<b046982c>] (bus_remove_driver+0x68/0xdc)
[  266.345660] [<b046982c>] (bus_remove_driver) from [<af06ad40>] (mmc_blk_exit+0xc/0x2cc [mmc_block])
[  266.348875] [<af06ad40>] (mmc_blk_exit [mmc_block]) from [<b01aee30>] (SyS_delete_module+0x1c4/0x254)
[  266.352068] [<b01aee30>] (SyS_delete_module) from [<b0108480>] (ret_fast_syscall+0x0/0x34)
[  266.355308] ---[ end trace f68728a0d3053b72 ]---

Fixes: 7c84b8b4

 ("mmc: block: bypass the queue even if usage is present for hotplug")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>