scsi: hisi_sas: fix logic bug when alloc device with MAX device num == 1

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

We find that when set HISI_SAS_MAX_ITCT_ENTRIES as 1, we don't evenallocate
one device. This does not comply with the code logic designed by us.

The log is as follows:

[ 3.565847] hsi_sas_v3_hw 0000:74:02.0: Adding to iommu group 0
[ 3.582037] scsi host0: hisi_sas_v3_hw
[ 4.794270] hisi_sas_v3_hw 0000:74:02.0: Enable MSI auo-affinity
[ 4.872986] hisi_sas_v3_hw 0000:74:02.0: phyup: phy5 link_rate=11
[ 4.879057] hisi_sas_v3_hw 0000:74:02.0: phyup: phy0 link_rate=11
[ 4.879117] sas: phy-0:5 added to port-0:0, phy_mask:0x20 (500e004aaaaaaa1f)
[ 4.885131] hisi_sas_v3_hw 0000:74:02.0: phyup: phy1 link_rate=11
[ 4.885145] sas: DOING DISCOVERY on port 0, pid:910
[ 4.891199] hisi_sas_v3_hw 0000:74:02.0: phyup: phy2 link_rate=11
[ 4.891203] hisi_sas_v3_hw 0000:74:02.0: phyup: phy3 link_rate=11
[ 4.891209] hisi_sas_v3_hw 0000:74:02.0: phyup: phy4 link_rate=11
[ 4.897510] hisi_sas_v3_hw 0000:74:02.0: fail alloc dev: max support 1 devices
[ 4.903335] hisi_sas_v3_hw 0000:74:02.0: phyup: phy6 link_rate=11
[ 4.903340] hisi_sas_v3_hw 0000:74:02.0: phyup: phy7 link_rate=11
[ 4.909402] sas: driver on host 0000:74:02.0 cannot handle device 500e004aaaaaaa1f, error:-22
[ 4.937404] sas: DONE DISCOVERY on port 0, pid:910, result:-22
[ 4.937409] sas: broadcast received: 0
[ 4.937410] sas: phy0 matched wide port0
[ 4.937414] sas: phy-0:0 added to port-0:0, phy_mask:0x21 (500e004aaaaaaa1f)
[ 4.937431] sas: DOING DISCOVERY on port 0, pid:910
[ 4.937581] hisi_sas_v3_hw 0000:74:02.0: fail alloc dev: max support 1 devices
[ 4.944774] sas: driver on host 0000:74:02.0 cannot handle device 500e004aaaaaaa1f, error:-22
[ 4.953395] sas: DONE DISCOVERY on port 0, pid:910, result:-22

We find that this extreme case is not considered when implementing
hisi_sas_alloc_dev(). Actually, the device ID is allocated from 1 instead
of 0. As a result, if the value of HISI_SAS_MAX_ITCT_ENTRIES is 1, the
driver considers that the number of devices has reached the upper limit and
return sas_dev with NULL.

Signed-off-by: Wang Chao <wangchao342@hisilicon.com>
Reviewed-by: Zhu Xiongxiong <zhuxiongxiong@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>