bnxt_en: Fix a variable scoping in bnxt_hwrm_do_send_msg()

short_input variable is assigned to another data pointer which is
referred out of its scope. Fix it by moving short_input definition
to the beginning of bnxt_hwrm_do_send_msg() function.

No failure has been reported so far due to this issue.

Fixes: e605db80 ("bnxt_en: Support for Short Firmware Message")
Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>