Normality for a substance is just the molarity that would be neutralized by the #"H"^(+)# from an incoming acid or #"OH"^(-)# from an incoming base that you could get if that substance dissociated completely.
Since there is only one #"H"^(+)# in #"HCl"#, #"0.1 N HCl"# #=# #"0.1 M HCl"#.
[If it was #"0.1 M H"_2"SO"_4#, then it would be #"0.2 N H"_2"SO"_4#, because #"0.2 M"# of #"OH"^(-)# is needed to neutralize #"0.1 M H"_2"SO"_4#.]
#"HCl"# is a strong acid, and it dissociates completely.
#"HCl"(aq) -> "H"^(+)(aq) + "Cl"^(-)(aq)#
Therefore, the molarity of #"HCl"#, or #["HCl"]#, is pretty much the same as #["H"^(+)]#.
#=> ["H"^(+)] = "0.1 M"#
It really doesn't matter what the volume is. #"pH"# depends on the concentration, not the mols.
#color(blue)("pH") = -log["H"^(+)]#
#= -log(0.1) = color(blue)(1)#
