Documentation: arm64/acpi : clarify arm64 support of IBFT

In commit 94bccc3 ("iscsi_ibft: make ISCSI_IBFT dependson ACPI instead
of ISCSI_IBFT_FIND") Kconfig was disentangled to make ISCSI_IBFT selection
not depend on x86.

Update arm64 acpi documentation, changing IBFT support status from
"Not Supported" to "Optional".
Opportunistically re-flow paragraph for changed lines.

Link: https://lore.kernel.org/lkml/1563475054-10680-1-git-send-email-thomas.tai@oracle.com/

Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Link: https://lore.kernel.org/r/9efc652df2b8d6b53d9acb170eb7c9ca3938dfef.1615920441.git.tom.saeger@oracle.com
Signed-off-by: Will Deacon <will@kernel.org>

Documentation/arm64/acpi_object_usage.rst

@@ -17,12 +17,12 @@ For ACPI on arm64, tables also fall into the following categories:
 
        -  Recommended: BERT, EINJ, ERST, HEST, PCCT, SSDT
 
-       -  Optional: BGRT, CPEP, CSRT, DBG2, DRTM, ECDT, FACS, FPDT, IORT,
-          MCHI, MPST, MSCT, NFIT, PMTT, RASF, SBST, SLIT, SPMI, SRAT, STAO,
-	  TCPA, TPM2, UEFI, XENV
+       -  Optional: BGRT, CPEP, CSRT, DBG2, DRTM, ECDT, FACS, FPDT, IBFT,
+          IORT, MCHI, MPST, MSCT, NFIT, PMTT, RASF, SBST, SLIT, SPMI, SRAT,
+          STAO, TCPA, TPM2, UEFI, XENV
 
-       -  Not supported: BOOT, DBGP, DMAR, ETDT, HPET, IBFT, IVRS, LPIT,
-          MSDM, OEMx, PSDT, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
+       -  Not supported: BOOT, DBGP, DMAR, ETDT, HPET, IVRS, LPIT, MSDM, OEMx,
+          PSDT, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
 
 ====== ========================================================================
 Table  Usage for ARMv8 Linux