xen/riscv: drop pregs from struct cpu_user_regs

As nothing is using pregs in upstream or downstream ports of RISC-V drop
it from struct cpu_user_regs. Once it will really be needed re-introduce
it.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Baptiste Le Duc <baptiste.le-duc@vates.tech>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/riscv/include/asm/processor.h

@@ -50,8 +50,6 @@ struct cpu_user_regs
     unsigned long sepc;
     unsigned long sstatus;
     unsigned long hstatus;
-    /* pointer to previous stack_cpu_regs */
-    unsigned long pregs;
 };
 
 /* TODO: need to implement */

xen/arch/riscv/riscv64/asm-offsets.c

@@ -50,7 +50,6 @@ void asm_offsets(void)
     OFFSET(CPU_USER_REGS_SEPC, struct cpu_user_regs, sepc);
     OFFSET(CPU_USER_REGS_SSTATUS, struct cpu_user_regs, sstatus);
     OFFSET(CPU_USER_REGS_HSTATUS, struct cpu_user_regs, hstatus);
-    OFFSET(CPU_USER_REGS_PREGS, struct cpu_user_regs, pregs);
     BLANK();
     DEFINE(PCPU_INFO_SIZE, sizeof(struct pcpu_info));
     BLANK();