matmul fails with ints on GPU

[coquelin77]

To Reproduce

import heat as ht

a = ht.random.randint(0, 30, size=(30, 30), device="gpu", split=0)
b = ht.random.randint(0, 30, size=(30, 30), device="gpu", split=0)
ht.dot(a, b)

result:

RuntimeError: "addmm_cuda" not implemented for 'Int'

Traceback (most recent call last):
  File "dot-test.py", line 5, in <module>
    ht.dot(a, b)
  File "/p/home/jusers/coquelin1/hdfml/heat/heat/heat/core/linalg/basics.py", line 56, in dot
    ret = matmul(a, b)
  File "/p/home/jusers/coquelin1/hdfml/heat/heat/heat/core/linalg/basics.py", line 501, in matmul
    c=c._DNDarray__array,
RuntimeError: The following operation failed in the TorchScript interpreter.
Traceback of TorchScript (most recent call last):
  File "/p/home/jusers/coquelin1/hdfml/heat/heat/heat/core/linalg/basics.py", line 803, in __mm_c_block_setter
                    c_start0 = a_start0
                    c_start1 = b_start1
                    c[c_start0 : c_start0 + mB, c_start1 : c_start1 + nB] += a_block @ b_block
                                                                             ~~~~~~~~~~~~~~~~~ <--- HERE
RuntimeError: "addmm_cuda" not implemented for 'Int'

Expected behavior
Should run without failure

Version Info
current master