cmd: hash: fix param count check

cmd: hash: fix param count check

Add correct check for parameter count.

This fixes this issue when `hash` cmd is invoked without params:

=> hash
data abort
pc : [<bf739204>]	   lr : [<ba6effa8>]
reloc pc : [<60019204>]	   lr : [<5afcffa8>]
sp : ba6dd9c8  ip : bf7391f0	 fp : bf74ec14
r10: 00000001  r9 : ba6dfea0	 r8 : bf7ea030
r7 : 00000000  r6 : ba6effa8	 r5 : 00000000  r4 : ffffffff
r3 : bf7c257c  r2 : 00000001	 r1 : 00000000  r0 : bf7e6e34
Flags: nZCv  IRQs off  FIQs on  Mode SVC_32
Code: e5934004 e1a0e003 e59f3050 e2444001 (e5f4c001)
Resetting CPU ...

resetting ...

Signed-off-by: Igor Opaniuk <igor.opaniuk@gmail.com>