LoongArch: uprobes: Remove redundant code about resume_era

arch_uprobe_skip_sstep() returns true if instruction was emulated, that
is to say, there is no need to single step for the emulated instructions.
regs->csr_era will point to the destination address directly after the
exception, so the resume_era related code is redundant, just remove them.

Cc: stable@vger.kernel.org
Fixes: 19bc6cb6 ("LoongArch: Add uprobes support")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>