ath10k: don't disable interrupts in ath10k_sdio_remove()

Disabling interrupts this early meant WMI communication was not working anymore
when the SDIO device was removed. But we call ath10k_core_unregister() that
will eventually call ath10k_sdio_hif_stop(), which disables the interrupts. So
there's actually no need to disable interrupts here.

Also remove cancel_work_sync() as it's also called in ath10k_sdio_hif_stop().

Tested with QCA6174 SDIO with firmware WLAN.RMH.4.4.1-00007-QCARMSWP-1.

Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>