MdeModulePkg/DxeCapsuleLibFmp: Fix compilation error

[nhivp]

Description

The commit "MdeModulePkg/DxeCapsuleLibFmp: Fix crash if no ESRT is found" leads to a compilation error in MdeModulePkg/Library/DxeCapsuleLibFmp/DxeCapsuleLib.inf. The issue occurs because the variable mDxeCapsuleLibReadyToBootEvent which is declared as extern does not exist, while it is defined in DxeCapsuleRuntime.c, a file not included in DxeCapsuleLib.inf. This patch is to fix this by moving the variable defintion to DxeCapsuleLib.c and declare it as extern in DxeCapsuleRuntime.c.

Reported-by: Gua Guo gua.guo@intel.com

• [ ] Breaking change?
  • Breaking change - Will this cause a break in build or boot behavior?
  • Examples: Add a new library class or move a module to a different repo.
• [ ] Impacts security?
  • Security - Does the change have a direct security impact?
  • Examples: Crypto algorithm change or buffer overflow fix.
• [ ] Includes tests?
  • Tests - Does the change include any explicit test code?
  • Examples: Unit tests or integration tests.

How This Was Tested

Integration Instructions

[mdkinney]

Fixes build break introduced by https://github.com/tianocore/edk2/pull/5692