drivers: net: can: free allocated memory in k61_spi_transaction function

When multiple CAN frames are sent and received, kernel encounters out of
memory issue as the memory allocated in k61_spi_transaction_function is not
deallocated. Hence, free the allocated memory to avoid memory leak.

CRs-Fixed: 2069680
Change-Id: Ic99a5e93f763dcdad41a1d3d418ff774189e0252
Signed-off-by: Abinaya P <abinayap@codeaurora.org>