lib: sbi: Add functions to manipulate PMP entries

- Add a function to disable a given PMP entry.
- Add a function to check if a given entry is disabled.

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

include/sbi/riscv_asm.h

@@ -181,6 +181,12 @@ int misa_xlen(void);
 /* Get RISC-V ISA string representation */
 void misa_string(int xlen, char *out, unsigned int out_sz);
 
+/* Disable pmp entry at a given index */
+int pmp_disable(unsigned int n);
+
+/* Check if the matching field is set */
+int is_pmp_entry_mapped(unsigned long entry);
+
 int pmp_set(unsigned int n, unsigned long prot, unsigned long addr,
 	    unsigned long log2len);