CryptoPkg/RuntimeDxeCryptLib: Make globals static (#741)

## Description

The GNU linker (ld) raises an error due to duplicate symbols for the
`mVirtualAddressChangeEvent` global. This change updates both globals
in the file to be static to prevent future symbol collisions.

- [ ] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

- Built `VariableRuntimeDxe` using GCC on Ubuntu with the
`RuntimeDxeCryptLib`
  library instance linked.

## Integration Instructions

N/A

Signed-off-by: Michael Kubacki <[email protected]>

CryptoPkg/Library/BaseCryptLibOnProtocolPpi/RuntimeDxeCryptLib.c

@@ -14,8 +14,8 @@
 #include <Library/UefiRuntimeLib.h>
 #include <Protocol/Crypto.h>
 
-EDKII_CRYPTO_PROTOCOL  *mCryptoProtocol           = NULL;
-EFI_EVENT              mVirtualAddressChangeEvent = NULL;
+STATIC  EDKII_CRYPTO_PROTOCOL  *mCryptoProtocol           = NULL;
+STATIC  EFI_EVENT              mVirtualAddressChangeEvent = NULL;
 
 /**
   Internal worker function that returns the pointer to an EDK II Crypto