tpm_crb: Use IOMEM_ERR_PTR when function returns iomem

This is to simplify the code, and IOMEM_ERR_PTR(err) is same with
(__force void __iomem *)ERR_PTR(err).

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>