staging: ks7010: Replace mdelay with usleep_range in ks7010_upload_firmware

ks7010_upload_firmware() is never called in atomic context.

The call chain ending up at ks7010_upload_firmware() is:
[1] ks7010_upload_firmware() <- ks7010_sdio_probe()

ks7010_sdio_probe() is set as ".probe" in struct sdio_driver.
This function is not called in atomic context.

Despite never getting called from atomic context, ks7010_upload_firmware()
calls mdelay() to busily wait.
This is not necessary and can be replaced with usleep_range() to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>