riscv: replace deprecated scall with ecall

scall is a deprecated alias for ecall. ecall is used in several places,
so there is no assembler compatibility concern.
Signed-off-by: Fangrui Song <maskray@google.com>
Link: https://lore.kernel.org/r/20230423223210.126948-1-maskray@google.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/entry.S

@@ -348,6 +348,6 @@ SYM_CODE_END(excp_vect_table)
 #ifndef CONFIG_MMU
 SYM_CODE_START(__user_rt_sigreturn)
 	li a7, __NR_rt_sigreturn
-	scall
+	ecall
 SYM_CODE_END(__user_rt_sigreturn)
 #endif

arch/riscv/kernel/vdso/rt_sigreturn.S

@@ -11,6 +11,6 @@ ENTRY(__vdso_rt_sigreturn)
 	.cfi_startproc
 	.cfi_signal_frame
 	li a7, __NR_rt_sigreturn
-	scall
+	ecall
 	.cfi_endproc
 ENDPROC(__vdso_rt_sigreturn)