riscv_internal.h: Remove riscv_sbi.h from the file

riscv_internal.h is used literally everywhere, while the SBI definitions
are needed only by whomever needs the services.

Having the SBI definitions:
a) Copied from OpenSBI (why has this been done? even the names are same)
b) Presented publicly to 99% of risc-v modules

creates a build error when building with OpenSBI, due to duplicate
definitions of the SBI service identifiers:

In file included from /nuttx/arch/risc-v/src/common/riscv_internal.h:40,
                 from /nuttx/arch/risc-v/src/chip/chip.h:32,
                 from board/mpfs_domain.c:30:
/nuttx/arch/risc-v/src/common/riscv_sbi.h:36: error: "SBI_EXT_BASE" redefined [-Werror]
   36 | #define SBI_EXT_BASE            0x00000010

and so forth...

Fix this by removing riscv_sbi.h i.e. not exposing the ABI publicly.

arch/risc-v/src/common/riscv_internal.h

@@ -37,7 +37,6 @@
 
 #include <nuttx/irq.h>
 
-#include "riscv_sbi.h"
 #include "riscv_common_memorymap.h"
 
 /****************************************************************************

arch/risc-v/src/common/riscv_ipi.h

@@ -26,6 +26,7 @@
  ****************************************************************************/
 
 #include "riscv_internal.h"
+#include "riscv_sbi.h"
 #include "chip.h"
 
 /****************************************************************************

arch/risc-v/src/common/riscv_mtimer.c

@@ -27,8 +27,9 @@
 
 #include <arch/barriers.h>
 
-#include "riscv_mtimer.h"
 #include "riscv_internal.h"
+#include "riscv_mtimer.h"
+#include "riscv_sbi.h"
 
 /****************************************************************************
  * Private Types

arch/risc-v/src/nuttsbi/sbi_mcall.c

@@ -28,6 +28,7 @@
 #include <stdint.h>
 
 #include "riscv_internal.h"
+#include "riscv_sbi.h"
 
 #include "sbi_mcall.h"
 #include "sbi_internal.h"

arch/risc-v/src/qemu-rv/qemu_rv_start.c

@@ -31,6 +31,7 @@
 
 #include <debug.h>
 #include "riscv_internal.h"
+#include "riscv_sbi.h"
 #include "chip.h"
 
 #include "qemu_rv_userspace.h"

boards/risc-v/qemu-rv/rv-virt/src/qemu_rv_appinit.c

@@ -41,6 +41,7 @@
 #include "qemu_rv_rptun.h"
 
 #include "riscv_internal.h"
+#include "riscv_sbi.h"
 #include "romfs.h"
 
 #ifdef CONFIG_USERLED