net: lib: midi2: fix reverse null dereference in auth_session

Coverity found a REVERSE_INULL defect (CID 551615).
The 'hasher' pointer was used before it was checked
for NULL in crypto_query_hwcaps().

This patch reorders the logic to check the pointer
immediately after device_get_binding().

Fixes CID 551615

Signed-off-by: Shreya Kulkarni <kulkarnishreya2421@gmail.com>