mtd: rawnand: diskonchip: Replace mdelay with usleep_range in doc_probe

doc_probe() is never called in atomic context.

doc_probe() is only called by init_nanddoc(), which is only set as
a parameter of module_init().
This function is not called in atomic context.

Despite never getting called from atomic context, doc_probe()
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: Boris Brezillon <boris.brezillon@bootlin.com>

drivers/mtd/nand/raw/diskonchip.c

@@ -1481,12 +1481,12 @@ static int __init doc_probe(unsigned long physadr)
 		WriteDOC(tmp, virtadr, Mplus_DOCControl);
 		WriteDOC(~tmp, virtadr, Mplus_CtrlConfirm);
 
-		mdelay(1);
+		usleep_range(1000, 2000);
 		/* Enable the Millennium Plus ASIC */
 		tmp = DOC_MODE_NORMAL | DOC_MODE_MDWREN | DOC_MODE_RST_LAT | DOC_MODE_BDECT;
 		WriteDOC(tmp, virtadr, Mplus_DOCControl);
 		WriteDOC(~tmp, virtadr, Mplus_CtrlConfirm);
-		mdelay(1);
+		usleep_range(1000, 2000);
 
 		ChipID = ReadDOC(virtadr, ChipID);