While going through the AHB5 specifications, I did'nt find RETY and SPLIT responses anywhere. Did ARM remove these responses?
Yes.
SPLIT and RETRY responses only existed in the first AHB spec (AMBA 2 AHB) where the single bus was supporting multiple masters and slaves. These responses allowed a slaves to tell the arbiter to possibly grant another master as the current request would stall the bus for too long.
However having lots of masters on a single bus was just a poor solution for performance because it didn't support parallel accesses, so most applications started moving to a single master per AHB "layer" approach, with a busmatrix supporting lots of these single master "layers" accessing mutiple shared slaves.
As each AHB layer then only had one possible master there was no need for master arbitration logic, and so SPLIT and RETRY reponses were then not needed. This solution was then officially documented as AHB-lite ("AMBA 3 AHB-lite" to use its full title).
AHB5 (AMBA 5 AHB) is essentially AHB-lite, with some added functions, so still a single master bus, with the expected mult-master support being added by a busmatrix component deciding which layer gets access to any slave shared between master layers, so still no need for SPLIT or RETRY response.
Hopefully that explains why these AHB2 responses disappeared.