**
Commit
d8ec2b183e9243366e3a0cd1116dbe879856b333
by kai.wang**[RISCV] Fix the calculation of the offset of Zvlsseg spilling.

For Zvlsseg spilling, we need to convert the pseudo instructions

into multiple vector load/store instructions with appropriate offsets.

For example, for PseudoVSPILL3_M2, we need to convert it to

VS2R %v2, %base

ADDI %base, %base, (vlenb x 2)

VS2R %v4, %base

ADDI %base, %base, (vlenb x 2)

VS2R %v6, %base

We need to keep the size of the offset in the pseudo spilling instructions.

In this case, it is (vlenb x 2).

In the original implementation, we use the size of frame objects divide the

number of vectors in zvlsseg types. The size of frame objects is not

necessary exactly the same as the spilling data. It may be larger than

it. So, we change it to (VLENB x LMUL) in this patch. The calculation is

more direct and easy to understand.

Differential Revision: https://reviews.llvm.org/D101869