Enable atomic mode support for SCMI SMC transport


Linux Kernel Configuration
└─>Device Drivers
└─>Firmware Drivers
└─>ARM System Control and Management Interface Protocol
└─>Enable atomic mode support for SCMI SMC transport
In linux kernel since version 5.2 (release Date: 2019-07-07)  
Enable support of atomic operation for SCMI SMC based transport.

If you want the SCMI SMC based transport to operate in atomic
mode, avoiding any kind of sleeping behaviour for selected
transactions on the TX path, answer Y.
Enabling atomic mode operations allows any SCMI driver using this
transport to optionally ask for atomic SCMI transactions and operate
in atomic context too, at the price of using a number of busy-waiting
primitives all over instead. If unsure say N.