drm/hisilicon: Fixed the warning: Assignment of 0/1 to bool variable

fixed the following warning:
hibmc_drm_drv.c:296:1-18:WARNING: Assignment of 0/1 to bool variable.
hibmc_drm_drv.c:301:2-19: WARNING: Assignment of 0/1 to bool variable.

v2:
using the pci_dev.msi_enabled instead of priv->msi_enabled.

v3:
just call pci_enable_msi() and pci_disable_msi(), it's no need to
set dev->pdev->msi_enabled again.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-By: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1595940907-17874-1-git-send-email-tiantao6@hisilicon.com