Fix USB MSC more than 2 LUNs support

[Igorbunow]

Add support more than 2 LUNs into USB MSC device

kernel: [ 1969.997185] scsi 8:0:0:0: Direct-Access     STM      MicroSD Device   0.01 PQ: 0 ANSI: 2
kernel: [ 1969.997830] scsi 8:0:0:1: Direct-Access     STM      EEPROM           0.01 PQ: 0 ANSI: 2
kernel: [ 1969.998390] scsi 8:0:0:2: Direct-Access     STM      System           0.01 PQ: 0 ANSI: 2
kernel: [ 1969.999059] scsi 8:0:0:3: Direct-Access     STM      Test             0.01 PQ: 0 ANSI: 2
kernel: [ 1969.999505] sd 8:0:0:0: Attached scsi generic sg7 type 0

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