lib: sbi_ecall: Add Kconfig option for each extension

For each SBI extension, we:

- Add a Kconfig option for it
- Add the extension to sbi_ecall_exts only if the extension is enabled
- Add the corresponding sbi_ecall_* object file only if the extension is
  enabled

Special cases are as follows:

- The legacy extensions are lumped together as one 'big' extension, as
  has always been the case in OpenSBI code.
- The platform-defined vendor extensions are regarded as one extension.
- The Base extension cannot be disabled.
- sbi_ecall_replace implements multiple extensions, so it's not easy to
  avoid linking it in. Enable it always, and use #ifdef to
  disable/enable individual extensions.

Signed-off-by: Vivian Wang <dramforever@live.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

lib/sbi/sbi_ecall_replace.c

@@ -19,6 +19,7 @@
 #include <sbi/sbi_tlb.h>
 #include <sbi/sbi_trap.h>
 
+#ifdef CONFIG_SBI_ECALL_TIME
 static int sbi_ecall_time_handler(unsigned long extid, unsigned long funcid,
 				  const struct sbi_trap_regs *regs,
 				  unsigned long *out_val,
@@ -43,7 +44,9 @@ struct sbi_ecall_extension ecall_time = {
 	.extid_end = SBI_EXT_TIME,
 	.handle = sbi_ecall_time_handler,
 };
+#endif
 
+#ifdef CONFIG_SBI_ECALL_RFENCE
 static int sbi_ecall_rfence_handler(unsigned long extid, unsigned long funcid,
 				    const struct sbi_trap_regs *regs,
 				    unsigned long *out_val,
@@ -113,7 +116,9 @@ struct sbi_ecall_extension ecall_rfence = {
 	.extid_end = SBI_EXT_RFENCE,
 	.handle = sbi_ecall_rfence_handler,
 };
+#endif
 
+#ifdef CONFIG_SBI_ECALL_IPI
 static int sbi_ecall_ipi_handler(unsigned long extid, unsigned long funcid,
 				 const struct sbi_trap_regs *regs,
 				 unsigned long *out_val,
@@ -134,7 +139,9 @@ struct sbi_ecall_extension ecall_ipi = {
 	.extid_end = SBI_EXT_IPI,
 	.handle = sbi_ecall_ipi_handler,
 };
+#endif
 
+#ifdef CONFIG_SBI_ECALL_SRST
 static int sbi_ecall_srst_handler(unsigned long extid, unsigned long funcid,
 				  const struct sbi_trap_regs *regs,
 				  unsigned long *out_val,
@@ -194,3 +201,4 @@ struct sbi_ecall_extension ecall_srst = {
 	.handle = sbi_ecall_srst_handler,
 	.probe = sbi_ecall_srst_probe,
 };
+#endif