Refine URT_040 requirement (ARC riscv-non-isa#201)

URT_040 merely states that non-volatile UEFI variables must be
persistent across reboots. This is redundant statement and the
requirement is not very clear. The intention of the requirement is to
mandate non-volatile UEFI variables. So, just make it is clear that UEFI
variables must be persistent.

Fixes: riscv-non-isa#201
Signed-off-by: Sunil V L <[email protected]>

uefi.adoc

@@ -79,7 +79,7 @@ See additional <<uefi-rt, requirements for UEFI runtime services>>.
              * `GetTime()` and `SetTime()` MUST be appropriately described in the `EFI_RT_PROPERTIES_TABLE`.
 | `URT_030` a| The UEFI `ResetSystem()` runtime service MUST be implemented.
 2+| _The OS MUST call the `ResetSystem()` runtime service call to reset or shutdown the system, preferring this to SBI, ACPI or other system-specific mechanisms. This allows for systems to perform any required system tasks on the way out (e.g. servicing `UpdateCapsule()` or persisting non-volatile variables in some systems)._
-| `URT_040` | Non-volatile UEFI variables MUST persist across calls to the `ResetSystem()` runtime service call.
+| `URT_040` | The UEFI variables MUST persist across calls to the `ResetSystem()` runtime service call.
 | `URT_050` | UEFI runtime services MUST be able to update the UEFI variables directly without the aid of an OS.
 2+| _UEFI variables are normally saved in a dedicated storage which is not directly accessible by the operating system._
 | `URT_060` a| The following requirements MUST be met for systems with UEFI secure boot: