[Fix] Update floormod simplification logic for better expression matching

[Ghosts381937]

Description

Update the floormod simplification rule to correctly handle expressions of the form floormod(c1*x, c2*x) by simplifying them to floormod(c1, c2). This enhancement enables better optimization of expressions that contain common factors, which frequently appear in transformer model computations.

Test Case

from tvm import tir
from tvm.arith import Analyzer
from tvm.tir.op import floormod

# Define symbolic variable
past_decoder_sequence_length = tir.Var("past_decoder_sequence_length", "int64")

# Create expressions with common factor
expr = tir.IntImm("int64", 64) * (past_decoder_sequence_length + tir.IntImm("int64", 1))
divisor = tir.IntImm("int64", 31) * (past_decoder_sequence_length + tir.IntImm("int64", 1))

# Create Analyzer
analyzer = Analyzer()

# Before: returns unsimplified expression
# After: correctly simplifies to 2
print(analyzer.simplify(floormod(expr, divisor)))