PCI: xgene-msi: Use bitmap_zalloc() when applicable

'xgene_msi->bitmap' is a bitmap. So use 'bitmap_zalloc()' to simplify code,
improve the semantic and avoid some open-coded arithmetic in allocator
arguments.

Also change the corresponding 'kfree()' into 'bitmap_free()' to keep
consistency.

Link: https://lore.kernel.org/r/32f3bc1fbfbd6ee0815e565012904758ca9eff7e.1635019243.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Krzysztof Wilczyński <kw@linux.com>

drivers/pci/controller/pci-xgene-msi.c

@@ -269,9 +269,7 @@ static void xgene_free_domains(struct xgene_msi *msi)
 
 static int xgene_msi_init_allocator(struct xgene_msi *xgene_msi)
 {
-	int size = BITS_TO_LONGS(NR_MSI_VEC) * sizeof(long);
-
-	xgene_msi->bitmap = kzalloc(size, GFP_KERNEL);
+	xgene_msi->bitmap = bitmap_zalloc(NR_MSI_VEC, GFP_KERNEL);
 	if (!xgene_msi->bitmap)
 		return -ENOMEM;
 
@@ -360,7 +358,7 @@ static int xgene_msi_remove(struct platform_device *pdev)
 
 	kfree(msi->msi_groups);
 
-	kfree(msi->bitmap);
+	bitmap_free(msi->bitmap);
 	msi->bitmap = NULL;
 
 	xgene_free_domains(msi);