Document portable_atomic_target_feature="zaamo" cfg

src/imp/interrupt/README.md

@@ -26,7 +26,7 @@ Some operations don't require disabling interrupts:
 
 - On architectures except for AVR: loads and stores with pointer size or smaller
 - On MSP430 additionally: {8,16}-bit `add,sub,and,or,xor,not`
-- On RISC-V with the `zaamo` target feature (or `force-amo` feature or `portable_atomic_force_amo` cfg) additionally: 32-bit(RV32)/{32,64}-bit(RV64) `swap,fetch_{add,sub,and,or,xor,not,max,min},add,sub,and,or,xor,not`, {8,16}-bit `fetch_{and,or,xor,not},and,or,xor,not`[^1], and all operations of `AtomicBool`
+- On RISC-V with the `zaamo` target feature (or `portable_atomic_target_feature="zaamo"` cfg or `force-amo` feature or `portable_atomic_force_amo` cfg) additionally: 32-bit(RV32)/{32,64}-bit(RV64) `swap,fetch_{add,sub,and,or,xor,not,max,min},add,sub,and,or,xor,not`, {8,16}-bit `fetch_{and,or,xor,not},and,or,xor,not`[^1], and all operations of `AtomicBool`
 
 However, when the `critical-section` feature is enabled, critical sections are taken for all atomic operations.