scsi: megaraid_sas: Create separate functions to allocate ctrl memory

commit 49a7a4adb0167b656b8dfb6ccb83220d553a1860 upstream.

No functional change. Code refactoring to improve readability.  Move the
code to allocate and free controller memory into separate functions.

Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>