x86: Handle {disp32} for (%bp)/(%ebp)/(%rbp)

Since (%bp)/(%ebp)/(%rbp) are encoded as 0(%bp)/0(%ebp)/0(%rbp), use
disp32/disp16 on 0(%bp)/0(%ebp)/0(%rbp) for {disp32}.

Note: Since there is no disp32 on 0(%bp), use disp16 instead.

	PR gas/26305
	* config/tc-i386.c (build_modrm_byte): Use disp32/disp16 on
	(%bp)/(%ebp)/(%rbp) for {disp32}.
	* doc/c-i386.texi: Update {disp32} documentation.
	* testsuite/gas/i386/pseudos.s: Add (%bp)/(%ebp) tests.
	* testsuite/gas/i386/x86-64-pseudos.s: Add (%ebp)/(%rbp) tests.
	* testsuite/gas/i386/pseudos.d: Updated.
	* testsuite/gas/i386/x86-64-pseudos.d: Likewise.

(cherry picked from commit 1a02d6b0)