There are (at least two) "generalizations" of Hölder inequality to the non-commutative case. One is the so called tracial matrix Hölder inequality: $$ |\langle A, B \rangle_{HS} |= |\mathrm{Tr} (A^\dagger B) | \le || A||_p \,\, || B||_q $$ where $|| A||_p$ is the Schatten $p$-norm and $1/p+1/q=1$. You can find a proof [here](http://arxiv.org/pdf/1106.6189v2.pdf). Another generalization is very similar to what you wrote and reads $$ \parallel \, |AB|\, \parallel \, \le\, \parallel \, |A|^p\, \parallel^{1/p} \,\, \parallel \, |B|^q\, \parallel^{1/q} $$ and it holds whenever $ \parallel \cdot \parallel$ is a unitarily invariant norm. You can find a proof in the book of Bhatia *Matrix Analysis*.