target/loongarch: Remove unnecessary page size validity checking

target/loongarch: Remove unnecessary page size validity checking

Page size of TLB entry comes from CSR STLBPS and pwcl register. With
huge page, it is dir_base + dir_width from pwcl register. With normal
page, it is field of PTBASE from pwcl register.

So it is ok to check validity in function helper_ldpte() and function
helper_csrwr_stlbps(). And it is unnecessary in tlb entry fill path.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>